Battery pack

ABSTRACT

Disclosed herein is a battery pack including: a plurality of cylindrical battery cells arranged in a plurality of rows and a plurality of layers; a partition member for partitioning the battery cells; and a casing for containing the battery cells partitioned by the partition member; wherein the material thickness of the casing is set to be larger than the material thickness of the partition member.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese PatentApplication JP 2007-130879 filed in the Japan Patent Office on May 16,2007, the entire contents of which being incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a battery pack with which it ispossible to enhance impact resistance performance.

2. Description of the Related Art

A battery pack includes a plurality of cylindrical battery cellsarranged in a plurality of rows and a plurality of layers, a partitionmember for partitioning the battery cells from each other, electrodetables for electrical connection between terminals of the battery cellspartitioned by the partition member, a lower case for containing thebattery cells electrically connected through the electrode tabs, and anupper cover for covering the lower case in which the battery cells arecontained, and is detachably attached to a body of an electronicapparatus, to be used as a power source for the electronic apparatus(refer to Japanese Patent Laid-Open No. 2003-257388).

In battery packs according to the related art, the material thicknessesof the lower case and the upper cover are set at minimum thicknessesconforming to the UL (Underwriters Laboratories Inc.) 94 Standard, forpromising a reduced size instead of a larger outer size. Therefore, inthe battery packs according to the related art, the material thicknessof the partition member is set to be larger than that of the casing, andenhancement of the impact resistance of the partition member forpartitioning the battery cells contained in the casing is contrived, soas to enhance the overall impact resistance performance.

Here, the battery packs for use in business-use electronic apparatusesneed to have a rated voltage of about 14.4 V, as contrasted to a ratedvoltage of about 7.2 V which is requisite for battery packs for use inprivate-use electronic apparatuses.

Therefore, in the case of the battery cell composed, for example, of acylindrical lithium ion secondary cell, the rated voltage of one batterycell is about 3.6 V, so that it suffices to connect two battery cells inseries in order to assemble a battery pack for use in private-useelectronic apparatuses needing the rated voltage of about 7.2 V. On theother hand, in order to assemble a battery pack for use in business-useelectronic apparatuses needing the rated voltage of about 14.4 V, fourbattery cells have to be connected in series. Thus, as compared with thebattery pack for business-use electronic apparatuses, the battery packfor business-use electronic apparatuses is larger in the number ofbattery cells, is heavier in weight, and is accompanied by a strongerneed for strength of the casing itself which is exposed to the exterior.

SUMMARY OF THE INVENTION

Thus, there is a need for a battery pack having an improved impactresistance performance.

In order to fulfill the above need, according to one embodiment of thepresent invention, there is provided a battery pack including: aplurality of cylindrical battery cells arranged in a plurality of rowsand a plurality of layers; a partition member for partitioning thebattery cells; and a casing for containing the battery cells partitionedby the partition member. In the battery pack, the material thickness ofthe casing is set to be larger that of the partition member.

According to the above embodiment of the invention, the materialthickness of the casing (which may include a lower case and an uppercover) is set to be larger than that of the partition member, whereby anenhanced strength of the casing is promised, and the impact resistanceperformance can be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are perspective views of an L-size battery pack based onthe present invention, wherein FIG. 1 is a front side perspective viewand FIG. 1B is a back side perspective view;

FIG. 2 is an exploded perspective view of the L-size battery pack basedon the invention;

FIGS. 3A and 3B are perspective views of an S-size battery pack based onthe invention, wherein FIG. 3A is a front side perspective view and FIG.3B is a back side perspective view;

FIG. 4 is a front view of a terminal part;

FIG. 5 is a side view of a video camera in which the battery pack basedon the invention is to be mounted;

FIG. 6 is a perspective view of the video camera to which the batterypack based on the invention is mounted;

FIGS. 7A and 7B are perspective views of a battery cell, wherein FIG. 7Ais a front side perspective view and FIG. 7B is a back side perspectiveview;

FIGS. 8A and 8B are perspective views of battery cells arranged in tworows and four layers, wherein FIG. 8A is a front side perspective viewand FIG. 8B is a back side perspective view;

FIG. 9 is an exploded perspective view of the battery cells arranged intwo rows and four layers;

FIG. 10 is a wiring diagram of the battery cells;

FIGS. 11A and 11B are side views of a partition member, wherein FIG. 11Ais a right side view and FIG. 11B is a left side view;

FIG. 12 is a bottom view of the partition member;

FIG. 13 is a plan view of the partition member;

FIGS. 14A and 14B are horizontal sectional views of the partitionmember, wherein FIG. 14A is a sectional view taken along line D-D ofFIG. 11A and FIG. 14B is a sectional view taken along line E-E of FIG.11A;

FIG. 15 is a side view of the battery cell;

FIGS. 16A and 16B are vertical sectional views of the partition member,wherein FIG. 16A is a sectional view taken along line F-F of FIG. 11Aand FIG. 16B is a sectional view taken along line G-G of FIG. 11A;

FIGS. 17A and 17B are perspective view of an essential part ofreinforcing ribs of the partition member, wherein FIG. 17A is anessential part perspective view of the reinforcing ribs formedcorrespondingly to the positive electrode terminal side of the batterycells and FIG. 17B is an essential part perspective view of thereinforcing ribs formed correspondingly to the negative electrodeterminal side of the battery cells;

FIG. 18 is a front view showing a welded condition of an electrode taband the battery cells;

FIG. 19 is a front view showing a welded condition of an electrode taband a battery cell according to the related art;

FIG. 20 is a diagram showing the distributions of weld strengthdepending on the presence/absence of a welding slit in an electrode tabincluding a nickel-plated copper plate;

FIG. 21 is a perspective view of an essential part of an electrode tabshowing a position matching hole having been subjected to burring;

FIG. 22 is a perspective view showing the condition where a terminalcase is mounted to a lower case;

FIG. 23 is a perspective view, partly broken, of a terminal part;

FIG. 24 is a perspective view, partly broken, of the condition where theterminal case is mounted to the lower case;

FIGS. 25A and 25B show the terminal case connected to battery cells anda main circuit board, wherein FIG. 25A is a front view and FIG. 25B is abottom view;

FIG. 26 is a perspective view showing the condition where the maincircuit board is mounted to the terminal case;

FIG. 27 is a side view showing the condition where the main circuitboard is mounted to the terminal case;

FIG. 28 is a vertical sectional view showing the main circuit board andthe terminal case disposed on the inside of the lower case;

FIGS. 29A to 29C are a plan view and sectional views of an upper cover,wherein FIG. 29A is the plan view of the upper cover, FIG. 29B is avertical sectional view along the major edge direction of the uppercover and FIG. 29C is a vertical sectional view along the minor edgedirection of the lower case;

FIGS. 30A to 30C are a plan view and sectional views of the lower case,wherein FIG. 30A is the plan view of the lower case, FIG. 30B is avertical sectional view along the major edge direction of the lower caseand FIG. 30C is a vertical sectional view along the minor edge directionof the lower case;

FIG. 31 is a front view of the partition member;

FIG. 32 is a vertical sectional view showing the condition where endparts of the upper cover and the lower case are opposed to and abuttedon each other and welded to each other;

FIG. 33 is an exploded perspective view of an S-size battery pack basedon the invention;

FIGS. 34A and 34B are perspective views of battery cells arranged in tworows and two layers, wherein FIG. 34A is a front side perspective viewand FIG. 34B is a back side perspective view;

FIG. 35 is an exploded perspective view of the battery cells arranged intwo rows and two layers; and

FIG. 36 is a wiring diagram of the battery cells arranged in two rowsand two layers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, a battery pack based on the present invention will be described indetail below, referring to the drawings. The battery pack based on thepresent invention is prepared in two kinds, according to the number ofbattery cells 8 contained in a casing 2, for example, an L-size batterypack 1 shown in FIGS. 1A, 1B and 2 and an S-size battery pack 100 shownin FIGS. 3A, 3B and 33. Specifically, the L-size battery pack 1 containseight battery cells 8 a to 8 h (hereinafter, the battery cells 8 a to 8h will also be referred to simply as the battery cells 8) in two rowsand four layers as shown in FIG. 2, while the S-size battery pack 100contains four battery cells 8 i to 8 l (hereinafter, the battery cells 8i to 8 l will also be referred to simply as the battery cells 8) in tworows and two layers as shown in FIG. 33. The battery packs 1, 100 basedon the present invention each have a roughly rectangular casing 2 inwhich the battery cells 8 are contained and which has a terminal part 6exposed at a front surface 2 b thereof.

As shown in FIG. 2, the casing 2 has an upper cover 3 and a lower case 4abutted on and joined to each other. In the casing 2, there arecontained a plurality of battery cells 8 including lithium ion secondarycells, a partition member 20 for partitioning the battery cells 8 fromone another, electrode tabs 30 for electrical connection among terminalsof the battery cells 8 partitioned by the partition member 20, aterminal case 40 provided with connection terminals for connection to anexternal apparatus, a main circuit board 50 attached to the terminalcase 40 and electrically connected to the battery cells 8 through theelectrode tabs 30, and a display circuit board 60 disposed on theopposite side of the main circuit board 50 with respect to the batterycells 8.

As shown in FIGS. 1A, 1B and 4, the casing 2 containing the batterycells 8 therein has a configuration in which a lower surface 2 a servesas a mount surface to be mounted to a battery mount part 5 on the sideof an electronic apparatus such as a video camera, and first to fifthterminal parts 6 a to 6 e are exposed at a front surface 2 b continuouswith the mount surface, from one side toward the other side in the widthdirection of the lower case 4. Terminals formed at the terminal parts 6a to 6 e are formed to have respective functions according to a serialinterface standard such as the SMBus (System Management Bus) interfacestandard. More specifically, the first terminal part 6 a is a positiveelectrode terminal of the battery pack 1, 100, the second terminal part6 b is a clock line terminal, the third terminal part 6 c is a data lineterminal, the fourth terminal part 6 d is an ID terminal to which an IDresistor is connected, and the fifth terminal part 6 e is a negativeelectrode terminal of the battery pack 1, 100.

In mounting the battery pack 1, 100 into an electronic apparatus, thebattery pack 1, 100 is inserted into the battery mount part 5 on theelectronic apparatus side, with the lower surface 2 a as an insertionend. After the lower surface 2 a comes to abut on a bottom surface ofthe battery mount part 5, the battery pack 1, 100 is slid toward theside of the front surface 2 b, whereby locking recesses 14, 15 providedat both side surfaces 2 c, 2 d of the casing 2 are locked on lockingprojections formed in the inside of the battery mount part 5, and thebattery pack 1, 100 is mounted in the electronic apparatus. Indismounting the battery pack 1, 100 from the electronic apparatus, thebattery pack 1, 100 is slid toward the side of a back surface 2 eopposite to the front surface 2 b of the casing 2, and is pulled uptoward the side of an upper surface 2 f opposite to the lower surface 2a, to be thereby dismounted from the electronic apparatus.

Examples of the electronic apparatus for which the battery pack 1, 100as above is to be used include a video camera 7 shown in FIG. 5. Thevideo camera 7 is for business use. As shown in FIG. 6, the video camera7 has a battery mount part 5 formed at a back surface 7 a of a mainbody. In consideration of the use time and frequency of the video camera7 for business use, the battery mount part 5 is so set that only abattery pack 1, 100 having a considerably high battery capacity can bemounted thereto.

Specifically, the battery pack 1, 100 for use in business-use electronicapparatuses needs to have a rated voltage of about 14.4 V, as contrastedto a rated voltage of about 7.2 V which is requisite for battery packsfor use in private-use electronic apparatuses. Besides, in the batterypack 1, 100 for use in business-use electronic apparatuses, the ratedvoltage of one battery cell 8 is about 3.6 V. Therefore, while itsuffices to connect two battery cells 8 in series in the battery packfor use in private-use electronic apparatuses needing the rated voltageof about 7.2 V, four battery cells 8 have to be connected in series inthe battery pack 1, 100 for use in business-use electronic apparatusesneeding the rated voltage of about 14.4 V. Thus, the battery pack 1, 100for business-use electronic apparatuses is larger in the number ofbattery cells 8 and is heavier, as compared with the battery pack forprivate-use electronic apparatuses.

As shown in FIG. 6, the battery pack 1, 100 is inserted into the batterymount part 5 of the video camera 7 in the direction of arrow A in FIG.6, with its lower surface 2 a as an insertion end and along the rightside of the back surface 7 a of the video camera 7, until it comes intoa loading/unloading position where its lower surface 2 a is abutted onthe bottom surface of the battery mount part 5. Next, in the batterymount part 5, the battery pack 1, 100 inserted into theloading/unloading position is slid in the direction of arrow B, i.e.,toward the left side in FIG. 6 until it comes to a mount position whereterminal pins (not shown) exposed in the inside of the battery mountpart 5 are inserted in the terminal part 6 provided at the front surface2 b of the battery pack 1, 100 and where locking recesses 14, 15provided at both side surfaces 2 c, 2 d are locked on lockingprojections (not shown) formed in the inside of the battery mount part5, whereby the mounting is completed.

Now, the configuration of the battery pack 1, 100 will be descried indetail below. First, the L-size battery pack 1 containing eight batterycells 8 a to 8 h in two rows and four layers therein will be described.

As shown in FIG. 2, the battery cells 8 a to 8 h contained in two rowsand four layers in the casing 2 of the L-size battery pack 1 are each acylindrical lithium ion secondary cell, as shown in FIGS. 7A and 7B. Thebattery cell 8 has: a cylindrical metal-made cell can which contains apositive electrode, a negative electrode, a separator and the liketherein, which is opened at one end in the longitudinal directionthereof and closed at the other end, and in which the closed other endas a whole serves as a negative electrode terminal 10 b; and a positiveelectrode cap which is welded to the open one end of the cell can andwhich serves as a positive electrode terminal 10 a, with an electrolytecontained in the cell can. In addition, as shown in FIGS. 7A and 7B, thebattery cell 8 has a structure in which a side surface 10 c, the outerperipheral surface of an end face of the positive electrode terminal 10a and the outer peripheral surface of an end face of the negativeelectrode terminal 10 b are covered with an insulating film. As shown inFIG. 7A, at the end face of the positive electrode terminal 10 a of thebattery cell 8, there is provided a positive electrode side covered part10 d having an outer peripheral surface covered with the insulating filmcovering the side surface 10 c, and, in a central area of the end face,the positive electrode terminal 10 a is exposed from the positiveelectrode side covered part 10 d. Besides, as shown in FIG. 7B, at theend face of the negative electrode terminal 10 b of the battery cell 8,there is provided a negative electrode side covered part 10 e having anouter peripheral surface covered with the insulating film covering theside surface 10 c, and, in a central area of the end face, the negativeelectrode terminal 10 b is exposed from the negative electrode sidecovered part 10 e.

The battery cells 8 as above are arranged in two rows and four layersover the main circuit board 50 so that their longitudinal axes aresubstantially parallel to the major edges of the main circuit board 50.Specifically, the battery cells 8 are arranged as shown in FIGS. 8A, 8Band 9, in which the first battery cell 8 a is disposed in the vicinityof a first terminal connection part 53 a (see FIG. 25B) which iselectrically connected to the first terminal part 6 a and which isdisposed on one side with respect to the width direction of the maincircuit board 50, the second battery cell 8 b is disposed over the firstbattery cell 8 a, the third battery cell 8 c is disposed over the secondbattery cell 8 b, and the fourth battery cell 8 d is disposed over thethird battery cell 8 c. In addition, of the battery cells 8, the fifthbattery cell 8 e is disposed in the vicinity of a fifth terminalconnection part 53 e (see FIG. 25B) which is electrically connected tothe fifth terminal part 6 e and which is disposed on the other side withrespect to the width direction of the main circuit board 50, the sixthbattery cell 8 f is disposed over the fifth battery cell 8 e, theseventh battery cell 8 g is disposed over the sixth battery cell 8 f,and the eighth battery cell 8 h is disposed over the seventh batterycell 8 g.

Besides, the first battery cell 8 a, the second battery cell 8 b, theseventh battery cell 8 g and the eighth battery cell 8 h are so arrangedthat their positive electrode terminals 10 a front on the terminal part6 side, i.e., on the front surface 2 b side. Further, the third batterycell 8 c, the fourth battery cell 8 d, the fifth battery cell 8 e andthe sixth battery cell 8 f are so arranged that their negative electrodeterminals 10 b front on the terminal part 6 side, i.e., on the frontsurface 2 b side.

Of the battery cells 8 arranged in two rows and four layers as above,four battery cells have to be connected in series because the batterypack 1 for use in a business-use electronic apparatus needs a ratedvoltage of about 14.4 V and each of the battery cells 8 has a ratedvoltage of about 3.6 V. In view of this, the battery cells 8 arepartitioned by the partition member 20, and terminals of the batterycells 8 are connected to one another through the electrode tabs 30;specifically, the battery cells 8 in each set of paired battery cellsare connected in parallel, and the four sets of the parallel-connectedpaired battery cells 8 are connected in series.

More specifically, in the arrangement of the battery cells 8, thepositive electrode terminal 10 a of the first battery cell 8 a disposedin the row on one side, the positive electrode terminal 10 a of thesecond battery cell 8 b and a first electrode tab connection part 52 aare electrically connected through a rectilinear first electrode tab 31.The first electrode tab 31 is fixed between the terminals by spotwelding, and its tip part 31 a is bent and soldered to the firstelectrode tab connection part 52 a.

In addition, in the arrangement of the battery cells 8, the negativeterminal 10 b of the first battery cell 8 a disposed in the row on oneside, the negative electrode terminal 10 b of the second battery cell 8b in the row, the positive electrode terminal 10 a of the third batterycell 8 c in the row and the positive electrode terminal 10 a of thefourth battery cell 8 d in the row are electrically connected through arectilinear second electrode tab 32. The second electrode tab 32 isfixed between the terminals by spot welding, and its tip part 32 a isbent and soldered to the second tab connection part 52 b.

Further, in the arrangement of the battery cells 8, the negativeelectrode terminal 10 b of the third battery cell 8 c disposed in therow on one side, the negative electrode terminal 10 b of the fourthbattery cell 8 d in the row, the positive electrode terminal 10 a of theseventh battery cell 8 g disposed in the row on the other side and thepositive electrode terminal 10 a of the eighth battery cell 8 h in therow are electrically connected through a roughly inverted U-shaped thirdelectrode tab 33. Specifically, the third electrode tab 33 has a firstconnection tab part 33 a through which the negative electrode terminal10 b of the third battery cell 8 c and the negative electrode terminal10 b of the fourth battery cell 8 d are electrically connected, and asecond connection tab part 33 b through which the positive electrodeterminal 10 a of the seventh battery cell 8 g and the positive electrodeterminal 10 a of the eighth battery cell 8 h are electrically connected.The first connection tab part 33 a and the second connection tab part 33b, together with a continuous tab part 33 c connecting them, form aroughly inverted U-shaped structure. In addition, the third electrodetab 32 is fixed between the terminals by spot welding.

Furthermore, in the arrangement of the battery cells 8, the positiveelectrode terminal 10 a of the fifth battery cell 8 e disposed in therow on the other side, the positive electrode terminal 10 a of the sixthbattery cell 8 f in the row, the negative electrode terminal 10 b of theseventh battery cell 8 g in the row and the negative electrode terminal10 b of the eighth battery cell 8 h in the row are electricallyconnected through a rectilinear fourth electrode tab 34. The fourthelectrode tab 34 is fixed between the terminals by spot welding, and itstip part 34 a is bent and soldered to the fourth electrode tabconnection part 52 d of the main circuit board 50.

In addition, in the arrangement of the battery cells 8, the negativeelectrode terminal 10 b of the fifth battery cell 8 e in the row on theother side, the negative electrode terminal 10 b of the sixth batterycell 8 f in the row and the fifth electrode tab connection part 52 e ofthe main circuit board 50 are electrically connected through arectilinear fifth electrode tab 35. The fifth electrode tab 35 is fixedbetween the terminals by spot welding, and its tip part 35 a is bent andsoldered to the fifth electrode tab connection part 52 e (hereinafter,the first to fifth electrode tabs 31 to 35 will also be referred tosimply as the electrode tabs 30, and their tip parts 31 a, 32 a, 34 a,35 a will also be referred to simply as the tip parts 30 a).

Incidentally, the third electrode tab 33 is not limited to the roughlyinverted U-shaped one, insofar as it provides continuation between thefirst connection tab part 33 a and the second connection tab part 33 b;for example, a roughly H-shaped electrode tab, a roughly U-shapedelectrode tab or the like may also be adopted.

In the battery cells 8 thus arranged in two rows and four layers, asshown in FIG. 10, the first battery cell 8 a and the second battery cell8 b are connected in parallel by the electrode tabs 30, next the thirdbattery cell 8 c and the fourth battery cell 8 d are connected inparallel by the electrode tabs 30, then the seventh battery cell 8 g andthe eighth battery cells 8 h are connected in parallel by the electrodetabs 30, and then the fifth battery cell 8 e and the sixth battery cell8 f are connected in parallel, whereby the battery cells 8 in each setof paired battery cells are connected in parallel, and the four sets ofthe parallel-connected paired battery cells 8 are sequentially connectedin series.

Consequently, in the battery pack 1 configured as above, the batterycells 8 having a rated voltage of about 3.6 V each are arranged in tworow and four layers over the main circuit board 50, the battery cells 8in each set of paired battery cells are connected in parallel, and thefour sets of the parallel-connected paired battery cells 8 aresequentially connected in series, whereby a rated voltage of about 14.4V can be realized, and the battery pack 1 can be used for business-useelectronic apparatuses such as video cameras.

In addition, in the battery pack 1, the area of the lower surface 2 aserving as a mount surface in mounting thereof into the battery mountpart 5 is equal to the area occupied by a pair of the battery cells 8.Therefore, the battery pack 1 has a reduced insertion area.

Besides, as shown in FIGS. 8A and 8B, the display circuit board 60 isdisposed on the partition member 20 at a position on the upper side ofthe fourth battery cell 8 d and the eighth battery cell 8 h. The displaycircuit board 60 is electrically connected to a board connection tabpart 33 d formed roughly at the midpoint of the continuous tab part 33 cof the third electrode tab 33. The board connection tab part 33 d isformed by bending in relation to the continuous tab part 33 c, and issoldered to a board connection part 63 of the display circuit board 60.Further, the display circuit board 60 is electrically connected to themain circuit board 50 through a flexible flat cable 36. Of the flexibleflat cable 36, one end is fixed to a cable connection part 64 of thedisplay circuit board 60, and the other end is electrically connected tothe third electrode tab connection part 52 c of the main circuit board50. This ensures that the third electrode tab 33 is electricallyconnected to the main circuit board 50 through the display circuit board60, without any complicated wiring or the like.

Here, the main circuit board 50 is provided with a voltage detectionunit 56 for detecting the voltage of each of the four sets of theparallel-connected paired battery cells 8, by use of a plurality ofelectronic parts such as IC chips. Since in the battery pack 1 the firstto fifth electrode tabs 31 to 35 are electrically connected to the maincircuit board 40 through the first to fifth electrode tab connectionparts 52 a to 52 e (hereinafter, the first to fifth electrode tabconnection parts 52 a to 52 e will also be referred to simply as theelectrode tab connection parts 52) as shown in FIG. 10, the voltage ofeach of the four sets of the parallel-connected paired battery cells 8can be detected by the voltage detection unit 56 of the main circuitboard 50, which makes it possible to check the residual batterycapacities of the battery cells 8, the presence or absence ofabnormality in the battery cells 8, etc.

In addition, as shown in FIG. 9, the partition member 20 forpartitioning the battery cells 8 includes: a roughly rectangularsheet-shaped partition plate 21; a positioning plate 22 which is formedat one side surface so as to be substantially orthogonal to theprincipal surface of the partition plate 21 and by which the maincircuit board 50 is positioned; an attaching plate 23 which is formed onthe other side of the partition plate 21, or the opposite side of thepositioning plate 22, and to which the display circuit board 60 isattached; a plurality of support plates 24 a to 24 f (hereinafter, thesupport plates 24 a to 24 f will also be referred to simply as thesupport plates 24) which are formed on both principal surfaces of thepartition member 20 at roughly regular intervals between the positioningplate 22 and the attaching plate 23 and by which the rows of the batterycells 8; and ribs 25 formed at corners formed between the partitionplate 21 and the support plates 24. The partition member 20 isintegrally formed from an insulating resin such as polypropylene. Thisensures that the battery cells 8 can be insulated from one another bythe partition member 20, without separately providing any insulatingmember or the like.

As shown in FIG. 9, the partition plate 21 is formed in a roughlyrectangular sheet-like shape. Of the principal surfaces of the partitionplate 21, the minor edges along which the positioning plate 22 and theattaching plate 23 are formed have a length approximately equal to thewhole length of the battery cell 8, and the major edges have a lengthapproximately equal to the overall height of the four layers in whichthe battery cells 8 are stacked. The partition plate 21 having suchprincipal surfaces is disposed between the row on one side of thebattery cells 8 arranged in two rows and four layers, specifically thefirst to fourth battery cells 8 a to 8 d, and the row on the other side,specifically the fifth to eighth battery cells 8 e to 8 h, so as topartition the battery cells 8 a to 8 d in the row on one side and thebattery cells 8 e to 8 h in the row on the other side from each other.

As shown in FIGS. 9, 11A and 11B, the positioning plate 22 formedintegrally with and substantially orthogonally to the principal surfacesof the partition plate 21 is formed at one minor edge of the partitionplate 21 in the state of substantially evenly projecting to bothprincipal surface sides of the partition plate 21 so as to besubstantially orthogonal to the principal surfaces of the partitionplate 21. The positioning plate 22 is formed in a roughly rectangularsheet-like shape having substantially the same size as the main circuitboard 50.

In addition, as shown in FIG. 12, the positioning plate 22 is formedwith positioning parts 26 a, 26 a and positioning projections 26 b forpositioning the main circuit board 50. The positioning parts 26 a, 26 aare mutually oppositely projectingly provided in roughly L-shaped forms,at positions on the side opposite to the side of attachment to theterminal case 40 of the principal surfaces of the main circuit board 50,namely, at positions corresponding respectively to both corner parts ofthe main circuit board 50 on the side of the back surface 2 e. Thepositioning parts 26 a, 26 a mutually oppositely projectingly providedin roughly L-shaped forms are operative to position the main circuitboard 50 by inserting the main circuit board 50 into the inside of thepositioning parts 26 a, 26 a. In addition, the positioning projection 26b is formed on a principal surface, on the side of facing the maincircuit board 50, of the positioning plate 22 so as to project towardthe side of the main circuit board 50, correspondingly to the layoutposition of a positioning hole 51 (see FIG. 9) which is a through-holeformed in the main circuit board 50. When the positioning projection 26b is inserted into the positioning hole 51, the main circuit board 50 ispositioned into such a plane orientation that it is parallel to thepositioning plate 22.

With the positioning parts 26 a, 26 a and the positioning projection 26b provided as above, in the process in which the tip parts 31 a, 32 a,34 a, 35 a of the first, second, fourth and fifth electrode tabs 31, 32,34, are soldered respectively to the first, second, fourth and fifthelectrode tab connection parts 52 a, 52 b, 52 c, 52 d of the maincircuit board 50, the main circuit board 50 is inserted on the innerside of the positioning parts 26 a, 26 a mutually oppositelyprojectingly provided in roughly L-shaped forms at positionscorresponding to both corner parts on the side of the back surface 2 eof the main circuit board 50, and then the positioning projection 26 bis inserted into the positioning hole 51 formed in the main circuitboard 50, by the manufacturer or the like, whereby the main circuitboard 50 can be easily positioned and arranged on the positioning plate22 without errors.

In addition, with the positioning parts 26 a, 26 a and the positioningprojection 26 b provided as above, even after the electrode tabs 30 aresoldered to the main circuit board 50, the main circuit board 50 ispositioned on the positioning plate 22 by inserting the main circuitboard 50 into the inner side of the positioning parts 26 a, 26 a andthen inserting the positioning projection 26 b into the positioning hole51 formed in the main circuit board 50, whereby the partition member 20can be prevented from sliding relative to the main circuit board 50 in adirection parallel to the main circuit board 50. Therefore, thepositioning parts 26 a, 26 a and the positioning projection 26 b canprevent the problem that a tensile load, a shearing load, a torsionalload or the like generated due to sliding of the partition member 20 isexerted on the electrode tab connection parts 52 to which the electrodetabs 30 are soldered, and can also prevent breakage of the electrodetabs 30 or the electrode tab connection parts 52 or the like fromoccurring. Incidentally, the positioning plate 22 may have either one ofthe positioning parts 26 a, 26 a and the positioning projection 26 b,insofar as the main circuit board 50 can be positioned.

In addition, the positioning plate 22 provided with the positioningparts 26 a, 26 a and the positioning projection 26 b is formedintegrally with the partition plate 21. Therefore, for example, insoldering the electrode tabs 30 to the electrode tab connection parts 52of the main circuit board 50, the main circuit board 50 can bepositioned without separately providing any positioning member, apositioning jig or the like for positioning the main circuit board 50relative to the positioning plate 22, so that the number of componentparts can be reduced.

Besides, the positioning plate 22 is provided substantially in thecenter of its principal surface facing the main circuit board 50 with aboard relief groove 22 a extending along its major edge direction overthe range from one minor edge thereof to the other minor edge thereof.The board relief groove 22 a is a recessed groove. This ensures thatelectronic parts such as IC chips can be mounted on the principalsurface, facing the positioning plate 22, of the main circuit board 50at positions in the area corresponding to the board relief groove 22 a.Therefore, electronic parts can be mounted on both principal surfaces ofthe main circuit board 50.

Further, since the positioning plate 22 is formed from an insulatingresin such as polypropylene, the main circuit board 50 can be insulatedfrom the battery cells 8 without interposing any insulating memberbetween the positioning plate 22 and the main circuit board 50, even inthe case where, for example, the main circuit board 50 is a printedcircuit board having conductor patterns on both sides or in multiplelayers.

In addition, the positioning plate 22 is provided with positioninggrooves 22 b correspondingly to the layout positions of case reinforcingribs 4 a formed on the inside of the lower case 4 which will bedescribed later. Since the positioning grooves 22 b are formedcorrespondingly to the layout positions of the case reinforcing ribs 4a, the partition member 20 can be positioned relative to the lower case4 and mis-insertion can be prevented, in containing the partition member20 into the inside of the lower case 4. Further, the positioning grooves22 b are engaged with the case reinforcing ribs 4 a, whereby thepartition member 20 can be prevented from sliding relative to the maincircuit board 50 along the principal surface of the latter. Therefore,the positioning grooves 22 can obviate the problem that a tensile load,a shearing load, a torsional load or the like generated due to slidingof the partition member 20 is exerted on the electrode tab connectionparts 52 to which the electrode tabs 30 are soldered, and can preventbreakage of the electrode tabs 30 or the electrode tab connection parts52 or the like from occurring.

As shown in FIGS. 9, 11A and 11B, the attaching plate 23 formedintegrally with the other minor edge, on the opposite side of thepositioning plate 22, of the partition plate 21 is formed to projectsubstantially evenly to both principal surface sides of the partitionplate 21 so as to be substantially orthogonal to the principal surfacesof the partition plate 21. The attaching plate 23 is formed in a roughlyrectangular sheet-like shape and in a size approximately equal to thesize of the display circuit board 60.

In addition, as shown in FIGS. 9 and 13, the attaching plate 23 isformed with engaging pieces 27 for positioning the display circuit board60. The engaging pieces 27 are engaged with the display circuit board60, whereby the display circuit board 60 is easily positioned relativeto the attaching plate 23 without errors, and the display circuit board60 in the positioned state is engagedly supported by the attaching plate23.

Therefore, the attaching plate 23 ensures that, at the time of solderinga board connection tab part 33 d of the third electrode tab 33 to aboard connection part 63 of the display circuit board 60 and connectingthe flexible flat cable 36 to a cable connection part 64 of the displaycircuit board 60, the display circuit board 60 can be easily positionedand attached without errors through engaging the display circuit board60 with the engaging pieces 27, the board connection tab part 33 d canbe soldered to the board connection part 63 of the display circuit board60 without errors, and the flexible flat cable 36 can be easilyconnected to the cable connection part 64 of the display circuit board60.

Besides, since the attaching plate 23 formed with such engaging pieces27 is formed as one body with the partition plate 21, the displaycircuit board 60 can be attached without separately providing anyattaching member or the like for attaching the display circuit board 60in the casing 2; thus, the number of component parts can be reduced.

Further, since the attaching plate 23 is formed from an insulating resinsuch as polypropylene, the battery cells 8 and the display circuit board60 can be insulated from each other without interposing any insulatingmember or the like between the attaching plate 23 and the displaycircuit board 60, even in the case where, for example, the displaycircuit board 60 is a printed circuit board having conductor patterns onboth sides or in multiple layers.

Incidentally, the attaching plate 23 is not limited to the one thatpositions the display circuit board 60 by engagement of its engagingpieces 27 with the display circuit board 60. For example, aconfiguration may be adopted in which the display circuit board 60 isprovided with through-holes, whereas the attaching plate 23 is providedwith positioning projections correspondingly to the layout positions ofthe through-holes, and the display circuit board 60 is positioned byinserting the positioning projections into the through-holes.

Here, the display circuit board 60 to be attached to the attaching plate23 is a printed wiring board including a rigid board provided withconductor patterns on one side, on both sides, in multiple layers, orthe like. Incidentally, the display circuit board 60 is not limited to arigid board, and may be a flexible board or the like. In addition, asshown in FIG. 9, on the display circuit board 60 are mounted lightemitting devices 61 including LEDs (Light Emitting Diodes) turned on toindicate the residual battery capacity of the battery pack 1, apushbutton type residual capacity display switch element 62 for turningon the light emitting devices 61, the board connection part 63 to beelectrically connected to the third electrode tab 33, and the cableconnection part 64 to be electrically connected to the main circuitboard 50.

In addition, since the display circuit board 60 is attached to theattaching part 23 and is disposed on the opposite side of the maincircuit board 50 with respect to the battery cells 8, the light emittingdevices 61 and the residual charge display switch element 62 are somounted as to be exposed to the exterior from the upper surface 2 f ofthe upper cover 3. Further, as shown in FIG. 8B, the display circuitboard 60 is electrically connected to the third electrode tab 33 bysoldering the board connection tab part 33 d of the third electrode tab33 to the board connection part 63, and is electrically connected to themain circuit board 50 through the flexible flat cable 36 by connectingone end of the flexible flat cable 36 to the cable connection part 64.

When the pushbutton type residual charge display switch element 62 isdepressed by the user or the like, the display circuit board 60 changesover the ON/OFF conditions of the light emitting devices 61 exposed tothe exterior through a display window 3 a formed in the upper surface 2f of the upper cover 3, as shown in FIG. 1, whereby the residual batterycharge is informed through the turned-ON display of the light emittingdevices 61. This permits the user to easily check the residual charge ofa spare battery pack not being mounted in an electronic apparatus suchas the video camera 7, to select a battery pack 1 with a large residualbattery charge or to distinguish such a battery pack from a battery pack1 with a smaller residual battery charge.

As shown in FIGS. 9, 11A and 11B, the support plates 24 provided betweenthe positioning plate 22 and the attaching plate 23 are projectinglyprovided on the principal surfaces of the partition plate 21, in thenumber of three on each of the principal surfaces and a total of six onboth the principal surfaces, substantially in parallel to thepositioning plate 22 and the attaching plate 23, i.e., substantiallyorthogonally to the principal surfaces of the partition plate 21 and atsubstantially regular intervals approximate to the diameter of thebattery cells 8 along the major edges (height direction) of thepartition plate 21. In addition, the support plates 24 are formed in aroughly rectangular sheet-like shape and are substantially evenlyprojected from the principal surfaces of the partition plate 21.

Specifically, on one principal surface of the partition plate 21, thefirst to third support plate 24 a to 24 c are formed in this order alongthe direction from the positioning plate 22 toward the attaching plate23. Similarly, on the other principal surface of the partition plate 21,the fourth to sixth support plates 24 d to 24 f are formed in this orderalong the direction from the positioning plate 22 toward the attachingplate 23. The support plates 24 formed on the principal surfaces of thepartition plate 21 partition each of the battery cells 8 a to 8 dpartition as one row by the partition plate 21, and partition each ofthe battery cells 8 e to 8 h partitioned as the other row by thepartition plate 21. More specifically, the first support plate 24 apartitions the first battery cell 8 a and the second battery cell 8 bfrom each other. The second support plate 24 b partitions the secondbattery cell 8 b and the third battery cell 8 c from each other. Thethird support plate 24 c partitions the third battery cell 8 c and thefourth battery cell 8 d from each other. The fourth support plate 24 dpartitions the fifth battery cell 8 e and the sixth battery cell 8 ffrom each other. The fifth support plate 24 e partitions the sixthbattery cell 8 f and the seventh battery cell 8 g from each other. Thesixth support plate 24 f partitions the seventh battery cell 8 g and theeighth battery cell 8 h from each other.

In other words, the first battery cell 8 a is disposed between the firstsupport plate 24 a and the positioning plate 22; the second battery cell8 b is disposed between the first support plate 24 a and the secondsupport plate 24 b; the third battery cell 8 c is disposed between thesecond support plate 24 b and the third support plate 24 c; the fourthbattery cell 8 d is disposed between the third support plate 24 c andthe attaching plate 23; the fifth battery cell 8 e is disposed betweenthe fourth support plate 24 d and the positioning plate 22; the sixthbattery cell 8 f is disposed between the fourth support plate 24 d andthe fifth support plate 24 e; the seventh battery cell 8 g is disposedbetween the fifth support plate 24 e and the sixth support plate 24 f;and the eighth battery cell 8 h is disposed between the sixth supportplate 24 f and the attaching plate 23.

In addition, as shown in FIGS. 8A and 8B, of the battery cells 8 whichare arranged in two rows and four layers and are partitioned by thepartition member 20 and of which the terminals are electricallyconnected through the electrode tabs 30, the third and fourth batterycells 8 c and 8 d disposed in the one-side row and the seventh andeighth battery cells 8 g and 8 h disposed in the other-side row areconnected in the manner of bridging between the one-side row and theother-side row through the roughly inverted U-shaped third electrode tab33. On the other hand, the first and second battery cells 8 a and 8 bdisposed in the one-side row and the fifth and sixth battery cells 8 eand 8 f disposed in the other-side row are not connected in the mannerof bridging between the one-side row and the other-side row, through therectilinear first, second, fourth and fifth electrode tabs 31, 32, 34,35, either on the front surface 2 b side or on the back surface 2 eside.

Further, as for the first and second battery cells 8 a and 8 b, thenegative electrode terminal 10 b of the first battery cell 8 a and thenegative electrode terminal 10 b of the second battery cell 8 b areconnected with the positive electrode terminal 10 a of the third batterycell 8 c and the positive electrode terminal 10 a of the fourth batterycell 8 d by the second electrode tab 32 on the back surface 2 e side.Also, as for the fifth and sixth battery cells 8 e and 8 f, the positiveelectrode terminal 10 a of the fifth battery cell 8 e and the positiveelectrode terminal 10 a of the sixth battery cell 8 f are connected withthe negative electrode terminal 10 b of the seventh battery cell 8 g andthe negative electrode terminal 10 b of the eighth battery cell 8 h bythe fourth electrode tab 34 on the back surface 2 e side. Therefore, forexample, when the battery pack is handled by the manufacturer's hand,the first and second battery cells 8 a and 8 b might be turned in thedirection of arrow C1 in FIG. 8A, with the second electrode tab 32 as acenter, in such a manner that the positive electrode terminal 10 a sideof the first and second battery cells 8 a and 8 b would come off fromthe partition member 20, resulting in loosening and dropping. Also, thefifth and sixth battery cells 8 e and 8 f might be turned in thedirection of arrow C2 in FIG. 8A, with the fourth electrode tab 34 as acenter, in such a manner that the negative electrode terminal 10 b sideof the fifth and sixth battery cells 8 e and 8 f would come off from thepartition member 20, resulting in loosening and dropping.

To avoid this possibility, the first and second battery cells 8 a, 8 band the fifth and sixth battery cells 8 e, 8 f are supported by thesupport plates 24 so that they would not be loosened and released fromthe partition member 20. In addition, the support plates 24 supportingthe first and second battery cells 8 a, 8 b and the fifth and sixthbattery cells 8 e, 8 f are demanded only to support either one of thefirst and second battery cell 8 a, 8 b because the first and secondbattery cells 8 a, 8 b are bound together by the first electrode tab 31on the front surface 2 b side, and the support plates 24 are demandedonly to support either one of the fifth and sixth battery cells 8 e, 8 fbecause the fifth and sixth battery cells 8 e, 8 f are bound together bythe fifth electrode tab 35 on the front surface 2 b side.

Here, FIG. 14A is a sectional view taken along line D-D of FIG. 11A, andFIG. 14B is a sectional view taken along line E-E of FIG. 11A. As shownin FIGS. 11A, 11B, 14A and 14B, the first support plate 24 a is formedwith a first projected piece 28 a for supporting the second battery cell8 b, the second support plate 24 b is formed with a second projectedpiece 28 b for supporting the second battery cell 8 b, the fourthsupport plate 24 d is formed with a third projected piece 28 c forsupporting the sixth battery cell 8 f, and the fifth support plate 24 eis formed with a fourth projected piece 28 d for supporting the sixthbattery cell 8 f (hereinafter, the first to fourth projected pieces 28 ato 28 d will also be referred to simply as the projected pieces 28).

The projected pieces 28 are formed to project further in the extensiondirection from the support plates 24. The first and second projectedpieces 28 a and 28 b adjacent to each other in the height directionsupport, by clamping therebetween, the side surface of the secondbattery cell 8 b which is disposed between the first and secondprojected pieces 28 a, 28 b. Similarly, the third and fourth projectedpieces 28 c and 28 d adjacent to each other in the height directionsupport, by clamping therebetween, the side surface of the sixth batterycell 8 which is disposed between the third and fourth projected pieces28 c, 28 d. In other words, the second battery cell 8 b is supportedwith its side surface clamped between the first projected piece 28 a andthe second projected piece 28 b, and the sixth battery cell 8 f issupported with its side surface clamped between the third projectedpiece 28 c and the fourth projected piece 28 d.

Accordingly, the projected pieces 28 ensure that, since the secondbattery cell 8 b and the sixth battery cell 8 f are supported by thesupport plates 24, the first and second battery cells 8 a, 8 b and thefifth and sixth battery cells 8 e, 8 f which are not connected by theelectrode tabs 30 over the range from one row to the other row, on thefront surface 2 b side and on the back surface 2 e side, can beprevented from becoming loosened and released from the support plates24.

Incidentally, the positioning plate 22 is not limited to theconfiguration in which one each of the first to fourth projected pieces28 a to 28 d is projected in the extension direction from each of thefirst, second, fourth and fifth support plates 24 a, 24 b, 24 c, 24 d,and a plurality of projected pieces may be projected from each of thesupport plates. This ensures that the second battery cell 8 b and thesixth battery cell 8 f are supported by the support plates 24 morerigidly, and the first and second battery cells 8 a, 8 b and the fifthand sixth battery cells 8 e, 8 f can be prevented from being loosenedand released from the support plates 24.

Incidentally, since the positioning plate 22 is projected substantiallyorthogonally to the partition plate 21, the positioning plate 22 maysupport the first battery cell 8 a by clamping it in cooperation withthe first projected piece 28 a, and may support the fifth battery cell 8e by clamping it in cooperation with the third projected piece 28 c.This ensures that the first and second battery cells 8 a, 8 b and thefifth and sixth battery cells 8 e, 8 f can be more securely preventedfrom being loosened and released from the support plates 24.

As shown in FIGS. 9, 11A and 11B, reinforcing ribs 25 aa to 25 de formedin respectively the corner formed between the partition plate 21 and thepositioning plate 22, the corners formed between the partition plate 21and the support plates 24, and the corner formed between the partitionplate 21 and the attaching plate 23 are formed, for example, in thenumber of five in each reinforcing rib set along the minor edgedirection of the partition plate 21. Specifically, the reinforcing ribsformed on the principal surface on one side of the partition member 20include the reinforcing ribs 25 aa to 25 ae formed in the corner formedbetween the partition plate 21 and the positioning plate 22 and thecorner formed between the partition plate 21 and the first support plate24 a, the reinforcing ribs 25 ba to 25 be formed in the corner formedbetween the partition plate 21 and the first support plate 24 a and thecorner formed between the partition plate 21 and the second supportplate 24 b, the reinforcing ribs 25 ca to 25 ce formed in the cornerformed between the partition plate 21 and the second support plate 24 band the corner formed between the partition plate 21 and the thirdsupport plate 24 c, and the reinforcing ribs 25 da to 25 de formed inthe corner formed between the partition plate 21 and the third supportplate 24 c and the corner formed between the partition plate 21 and theattaching plate 23. Similarly, the reinforcing ribs formed on theprincipal surface on the other side of the partition member 20, thereinforcing ribs 25 ea to 25 ee formed in the corner formed between thepartition plate 21 and the positioning plate 22 and the corner formedbetween the partition plate 21 and the fourth support plate 24 d, thereinforcing ribs 25 fa to 25 fe formed in the corner formed between thepartition plate 21 and the fourth support plate 24 d and the cornerformed between the partition plate 21 and the fifth support plate 24 e,the reinforcing ribs 25 ga to 25 ge formed between the partition plate21 and the fifth support plate 24 e and the corner formed between thepartition plate 21 and the sixth support plate 24 f, and the reinforcingribs 25 ha to 25 he formed in the corner formed between the partitionplate 21 and the sixth support plate 24 f and the corner formed betweenthe partition plate 21 and the attaching plate 23. Thus, the 20reinforcing ribs 25 aa to 25 de are formed on the principal surface onone side of the partition member 20, the 20 reinforcing ribs 25 ea to 25he are formed on the principal surface on the other side of thepartition member 20, and a total of 40 reinforcing ribs are formed(hereinafter, the reinforcing ribs 25 aa to 25 de and the reinforcingribs 25 ea to 25 he will also be referred to simply as the reinforcingribs 25).

As a result, the reinforcing ribs 25 enhance the mechanical strength ofthe partition plate 21, the positioning plate 22, the attaching plate 23and the support plates 24 and the like, whereby they can be preventedfrom deformation or the like, and an enhanced impact resistanceperformance of the partition member 20 can be contrived. Incidentally,the number of the reinforcing ribs 25 in each reinforcing rib set alongthe minor edge direction of the partition plate 21 is not limited tofive, and may be changed, as demanded, insofar as each part of thepartition member 20 can be reinforced.

In addition, the reinforcing ribs 25 da to 25 de formed in the cornerformed between the one-side principal surface of the partition plate 21and the third support plate 24 c and the corner formed between theone-side principal surface of the partition plate 21 and the attachingplate 23 and the reinforcing ribs 25 ha to 25 he formed in the cornerformed between the other-side principal surface of the partition plate21 and the sixth support plate 24 f and the corner formed between theother-side principal surface of the partition plate 21 and the attachingplate 23, particularly, reinforce the attaching plate 23 and prevent theattaching plate 23 from deformation or the like. Consequently, thereinforcing ribs 25 da to 25 de and the reinforcing ribs 25 ha to 25 hecan prevent the attaching plate 23 (which is a part receiving apressure, particularly) from deformation or the like under the pressureexerted on the attaching plate 23 when the residual charge displayswitch element 62 mounted on the display circuit board 60 attached tothe attaching plate 23 is depressed by the user or the like.

Further, the reinforcing ribs 25 are so located that the interval of thereinforcing ribs 25 on the side where the residual charge display switchelement 62 is mounted, along respect to the minor edge direction of thepartition plate 21, is gradually reduced as compared with that of thereinforcing ribs 25 on the side where the residual charge display switchelement 62 is not mounted. This enhances the mechanical strength of thepartition member 20 against the pressure exerted on the partition member20 when the residual charge display switch element 62 mounted on thedisplay circuit board 60 is depressed by the user or the like.Therefore, the partition member 20 can be prevented from deformation orthe like under the pressure exerted on the partition member 20 when theresidual charge display switch element 62 mounted on the display circuitboard 60 is depressed by the user or the like.

Specifically, in this embodiment, the residual display switch element 62mounted on the display circuit board 60 is located on the back surface 2e side, as shown in FIG. 2. In view of this, as shown in FIG. 11B, thereinforcing ribs 25 aa to 25 de formed on the one-side principal surfaceof the partition plate 21 are so located that the interval w1 betweenthe reinforcing ribs 25 aa, 25 ba, 25 ca, 25 da and the reinforcing ribs25 ab, 25 bb, 25 cb, 25 db, the interval w2 between the reinforcing ribs25 ab, 25 bb, 25 cb, 25 db and the reinforcing ribs 25 ac, 25 bc, 25 cc,25 dc, the interval w3 between the reinforcing ribs 25 ac, 25 bc, 25 cc,25 dc and the reinforcing ribs 25 ad, 25 bd, 25 cd, 25 dd, and theinterval w4 between the reinforcing ribs 25 ad, 25 bd, 25 cd, 25 dd andthe reinforcing ribs 25 ae, 25 be, 25 ce, 25 de are gradually decreasedin the order of the interval w1, interval w2, interval w3, and intervalw4, in the direction from the interval of the reinforcing ribs 25 on thefront surface 2 b side where the residual charge display switch element62 is not mounted toward the interval of the reinforcing ribs 25 on theback surface 2 e side where the residual charge display switch element62 is mounted.

Similarly, as shown in FIG. 11A, the reinforcing ribs 25 ea to 25 heformed on the other-side principal surface of the partition plate 21 areso located that the interval w5 between the reinforcing ribs 25 ea, 25fa, 25 ga, 25 ha and the reinforcing ribs 25 eb, 25 fb, 25 gb, 25 hb,the interval w6 between the reinforcing ribs 25 eb, 25 fb, 25 gb, 25 hband the reinforcing ribs 25 ec, 25 fc, 25 gc, 25 hc, the interval w7between the reinforcing ribs 25 ec, 25 fc, 25 gc, 25 hc and thereinforcing ribs 25 ed, 25 fd, 25 gd, 25 hd, and the interval w8 betweenthe reinforcing ribs 25 ed, 25 fd, 25 gd, 25 hd and the reinforcing ribs25 ee, 25 fe, 25 ge, 25 he are gradually decreased in the order of theinterval w5, interval w6, interval w7, and interval w8, in the directionfrom the interval of the reinforcing ribs 25 on the front surface 2 bside where the residual charge display switch element 62 is not mountedtoward the interval of the reinforcing ribs 25 on the back surface 2 eside where the residual charge display switch element 62 is mounted.

Therefore, since the reinforcing ribs 25 are formed at a reducedinterval on the side where the residual charge display switch element 62is mounted, the mechanical strength of the portion, on which a pressureis exerted when the residual charge display switch element 62 isdepressed by the user or the like, of the partition member 20 and thesurroundings can be enhanced concentratedly, and the partition member 20can be prevented from deformation or the like under the pressure.

Incidentally, the manner in which the reinforcing ribs 25 are formed isnot limited to the configuration in which the interval of thereinforcing ribs 25 is gradually decreased from the side where theresidual charge display switch element 62 is not mounted toward the sidewhere the residual charge display switch element 62 is mounted, insofaras the mechanical strength of the portion, on which the pressure isexerted when the residual charge display switch element 62 is depressedby the user or the like, of the partition member 20 and the surroundingscan be enhanced concentrically. Thus, a configuration may be adopted inwhich only the interval of the reinforcing ribs 25 at and around theposition where the residual charge display switch element is mounted isreduced.

In addition, as shown in FIG. 9, the reinforcing ribs 25 are each formedin a curved shape corresponding to the outer shape of the battery cell8, for supporting the battery cells 8 disposed between them and thesupport plates 24.

As shown in FIG. 15, the battery cell 8 has such a shape that its outersize on the positive electrode terminal 10 a side is greater than thaton the negative electrode terminal 10 b side. This is because thebattery cell 8 is expanded in the radial direction when the positiveelectrode cap constituting the positive electrode terminal 10 a iswelded to the cell can of the battery cell 8. Specifically, the batterycell 8 has a shape in which its outer size d1 on the positive electrodeterminal 10 a side is greater than its outer size d2 on the negativeelectrode terminal 10 b side by about 0.2 mm.

In view of this, the reinforcing ribs 25 are formed correspondingly tothe outer sizes d1, d2 which are different on the positive electrodeterminal 10 a side and the negative electrode terminal 10 b side of thebattery cell 8. Specifically, the reinforcing ribs 25 corresponding tothe positive electrode terminal 10 a side of the battery cell 8 areformed in a curved shape with an inner diameter d3 corresponding to theouter size d1 on the positive electrode terminal 10 a side, whereas thereinforcing ribs 25 corresponding to the negative electrode terminal 10b side are formed in a curves shape with an inner diameter d4corresponding to the outer size d2 on the negative electrode terminal 10b side. The inner diameter d3 of the reinforcing rib 25 is greater thanthe inner diameter d4 by about 0.2 mm, correspondingly to the fact thatthe outer size d1 on the positive electrode terminal 10 a side isgreater than the outer size d2 on the negative electrode terminal 10 bside by about 0.2 mm.

More specific description will be made by taking as an example the row(set) of the reinforcing ribs 25 ha to 25 he formed in the corner formedbetween the other-side principal surface of the partition plate 21 andthe sixth support plate 24 f and the corner formed between theother-side principal surface of the partition plate 21 and the attachingplate 23. As shown in FIGS. 8A and 8B, the eighth battery cell 8 hdisposed between the sixth support plate 24 f and the attaching plate 23is so disposed that its positive electrode terminal 10 a fronts on theterminal part 6 side, i.e., on the front surface 2 b side. Here, FIG.16A is a sectional view taken along line F-F of FIG. 11A, and FIG. 16Bis a sectional view taken along line G-G of FIG. 11A.

As shown in FIGS. 11A and 16A, the reinforcing ribs 25 ha to 25 hccorresponding to the positive electrode terminal 10 a side of the eighthbattery cell 8 h so disposed that its positive electrode terminal 10 afronts on the front surface 2 b side are formed in a curved shape withthe inner diameter d3 corresponding to the outer diameter d1 on thepositive electrode terminal 10 a side of the battery cell 8. As aresult, as shown in FIG. 17A, the reinforcing ribs 25 ha to 25 hc formedin the curved shape with the inner diameter d3 are provided on thesupport plate 24 in the state of not reaching the positions on thetongue pieces 29 which are formed to project in the extension directionfrom the support plate 24.

In addition, as shown in FIG. 16B, the reinforcing ribs 25 hd, 25 hecorresponding to the negative electrode terminal 10 b side of the eighthbattery cell 8, other than the reinforcing ribs 25 ha to 25 hccorresponding to the positive electrode terminal 10 a side of thebattery cell 8, are formed in a curved shape with the inner diameter d4corresponding to the outer size d2 on the negative electrode terminal 10b side of the battery cell 8. As a result, as shown in FIG. 17B, thereinforcing ribs 25 hd, 25 he formed in the curved shape with the innerdiameter d4 are provided to reach the positions on the tongue pieces 29formed to project in the extension direction from the support plate 24.

Similarly, the rows (sets) of the reinforcing ribs 25 aa to 25 ae, 25 bato 25 be, 25 ga to 25 ge are configured correspondingly to thearrangement in which the positive electrode terminals 10 a of the first,second and seventh battery cells 8 a, 8 b, 8 g front on the terminalpart 6 side, i.e., on the front surface 2 b side. Specifically, thereinforcing ribs 25 aa to 25 ac, 25 ba to 25 bc, 25 ga to 25 gccorresponding to the positive electrode terminal 10 a side of the first,second and seventh battery cells 8 a, 8 b, 8 g are formed in a curvedshape with the inner diameter d3 corresponding to the outer size d1 onthe positive electrode terminal 10 a side of the battery cell 8, in thesame manner as the reinforcing ribs 25 ha to 25 hc, whereas thereinforcing ribs 25 ad, 25 ae, 25 bd, 25 be, 25 gd, 25 ge correspondingto the negative electrode terminal 10 b side of the first, second andseventh battery cells 8 a, 8 b, 8 g are formed in a curved shape withthe inner diameter d4 corresponding to the outer size d2 on the negativeelectrode terminal 10 b side of the battery cell 8, in the same manneras the reinforcing ribs 25 hd, 25 he.

In addition, the rows (sets) of the reinforcing ribs 25 ca to 25 ce, 25da to 25 de, 25 ea to 25 ee, 25 fa to 25 fe are configuredcorrespondingly to the arrangement in which the positive electrodeterminals 10 a of the third, fourth, fifth and sixth battery cells 8 c,8 d, 8 e, 8 f front on the opposite side of the terminal parts 6, i.e.,on the back surface 2 e side. Specifically, the reinforcing ribs 25 cbto 25 ce, 25 db to 25 de, 25 eb to 25 ee, 25 fb to 25 fe correspondingto the positive electrode terminals 10 a of the third, fourth, fifth andsixth battery cells 8 c, 8 d, 8 e, 8 f are formed in a curved shape withthe inner diameter d3 corresponding to the outer size d1 on the positiveelectrode terminal 10 a side of the battery 8, in the same manner as thereinforcing ribs 25 ha to 25 hc, whereas the reinforcing ribs 25 ca, 25da, 25 ea, 25 fa corresponding to the negative electrode terminals 10 bof the third, fourth, fifth and sixth battery cells 8 c, 8 d, 8 e, 8 fare formed in a curves shape with the inner diameter d4 corresponding tothe outer size d2 on the negative electrode terminal 10 b side of thebattery cell 8, in the same manner as the reinforcing ribs 25 hd, 25 he.

Thus, the reinforcing ribs 25 are configured correspondingly to theouter sizes d1, d2 which are different on the positive electrodeterminal 10 a side and the negative electrode terminal 10 b side of thebattery cell 8. Therefore, the battery cells 8 can be supported inbetter contact with the reinforcing ribs 25, and the battery cells 8 canbe supported without chattering.

In addition, the reinforcing ribs 25 are so configured that at least thereinforcing ribs 25 formed on the most front surface 2 b and backsurface 2 e sides and corresponding to the outer diameter d1 on thepositive electrode terminal 10 a side of the battery cells 8 are formedto be greater in diameter than the other reinforcing ribs 25. Therefore,in assembling the battery cells 8 onto the partition member 20, thebattery cells 8 can be easily inserted between the support plates 24,with their negative electrode terminal 10 b side as the insertion end.

Incidentally, the reinforcing ribs 25 are not limited to theabove-mentioned configuration in which the reinforcing ribs 25 aa to 25ac, 25 ba to 25 bc, 25 cb to 25 ce, 25 db to 25 de, 25 eb to 25 ee, 25fb to 25 fe, 25 ga to 25 gc, 25 ha to 25 hc are formed in the curvedshape with the inner diameter d3, and the other reinforcing ribs 25 ad,25 ae, 25 bd, 25 be, 15 ca, 25 da, 25 ea, 25 fa, 25 gd, 25 ge, 25 hd, 25he are formed in the curved shape with the inner diameter d4. Theconfiguration may be changed, as demanded, insofar as the reinforcingribs are formed correspondingly to the outer sizes d1, d2 which aredifferent on the positive electrode terminal 10 a side and the negativeelectrode terminal 10 b side of the battery cells 8 and the batterycells 8 can be thereby supported without chattering.

Besides, the reinforcing ribs 25 are not limited to the curved shapeswith the inner diameters d3, d4, insofar as they can support the batterycells 8 without chattering. For example, the reinforcing ribs 25 may beformed with the inner diameters set corresponding to the respectiveouter sizes of the battery cell 8 at the positions where the batterycell 8 is supported by the reinforcing ribs 25.

The electrode tabs 30 for electrical connection between the terminals ofthe battery cells 8 partitioned and supported by the partition member 20as above-described are fixed to the terminal surfaces of the batterycells 8 by spot welding, as shown in FIGS. 8A and 8B. In addition, asshown in FIG. 18, the electrode tab 30 fixed to the terminals of thebattery cells 8 by spot welding is formed with a slit 39 along thelongitudinal direction thereof, between sets of weld fixation parts 38 ato 38 d (hereinafter, the weld fixation parts 38 a to 38 d will also bereferred to simply as the weld fixation parts 38) at the terminals ofthe battery cells 8, and with load absorbing parts 39 a, 39 a at bothends in the width direction of the slit 39. The slit 39 is formed in theshape of a slot (oblong hole), for example. The load absorbing parts 39a, 39 a serve to provide electrical connection between the sets of theweld fixation parts 38 at the terminals of the battery cells 8. Theelectrode tab 30 thus provided with the slit 39 and the load absorbingparts 39 a, 39 a is so provided that, due to the presence of the slit39, the load absorbing parts 39 a, 39 a provided at both ends in thewidth direction of the slit 39 are lower in rigidity than the otherparts, particularly, the weld fixation parts 38.

This ensures that, for example, in the case where the battery pack 1 isdropped or in the like situation, the impact load generated due to thedropping of the battery pack 1 is concentrated in the load absorbingparts 39 a, 39 a, so that the electrode tab 30 is plastically orelastically deformed at the load absorbing parts 39 a, 39 a. Therefore,the load on the electrode tab 30 is concentrated on the load absorbingparts 39 a, 39 a so provided as to be lower in rigidity than the otherparts, whereby the load can be prevented from being concentrated on theweld fixation parts 38 fixing the battery cells 8 and the electrode tab30, and the load exerted on the weld fixation parts 38 are moderated,whereby the weld fixation parts 38 can be prevented from rupture or thelike.

In addition, the slit 39 and the load absorbing parts 39 a, 39 a areformed roughly at a middle position between the sets of weld fixationparts 38 for the terminals of the battery cells 8. This ensures that theload is prevented from being concentrated on the load absorbing parts 39a, 39 a provided at both end parts in the width direction of the slit39, and the load is exerted substantially evenly on the load absorbingparts 39 a, 39 a, whereby the load absorbing parts 39 a, 39 a areprevented from rupture or the like. Therefore, since the electrode tab30 is provided with the slit 39 and the load absorbing parts 39 a, 39 aroughly at the middle position between the sets of the weld fixationparts 38 for the terminals of the battery cells 8, the load is exertedsubstantially evenly on the load absorbing parts 39 a, 39 a, and theload exerted on the weld fixation parts 38 can be moderatedsubstantially evenly, so that the weld fixation parts 38 can beprevented from rupture or the like.

Besides, the slit 39 is formed roughly at the center in the widthdirection of the electrode tab 30. This ensures that in the electrodetab 30, the load absorbing parts 39 a, 39 a provided at both end partsin the width direction of the slit 39 are substantially equal in width,so that concentration of a load on the load absorbing part 39 a on oneside is prevented from occurring. In addition, since the load is exertedevenly on the load absorbing parts 39 a, 39 a, the load absorbing parts39 a, 39 a are prevented from rupture or the like. Thus, since theelectrode tab 30 is provided with the slit 39 roughly at the center inthe width direction thereof and the load absorbing parts 39 a, 39 a havesubstantially equal widths, the load is exerted substantially evenly onthe load absorbing parts 39 a, 39 a, the load exerted on the weldfixation parts 38 can be moderated evenly, and the weld fixation parts38 can be prevented from rupture or the like.

In addition, the slit 39 is formed in such a length that the both endparts 39 b, 39 b thereof are located on the outside of a positiveelectrode side covered part 10 d, where an outer peripheral part of theend face of the positive electrode terminal 10 a of the battery cell 8is covered with an insulating film, and a negative electrode sidecovered part 10 e, where an outer peripheral part of the end face of thenegative electrode terminal 10 b of the battery cell 8 is covered withan insulating film. This ensures that both end parts 39 b, 39 b of theslit 39 in the electrode tab 30 do not overlap with the positiveelectrode terminal 10 a exposed from the positive electrode side coveredpart 10 d or with the negative electrode terminal 10 b exposed from thenegative electrode side covered part 10 e, so that the welding area atthe time of spot welding of the electrode tab 30 to the positiveelectrode terminal 10 a or the negative electrode terminal 10 b of thebattery cell 8 can be prevented from being reduced.

Besides, the electrode tabs 30 each includes a copper plate which isplated with nickel. Consequently, the electrode tabs 30 are lower inoverall rigidity than the nickel electrode tabs which have hitherto beenused. Therefore, the electrode tab 30 is formed to be low in overallrigidity, and the load thereon is concentrated on the load absorbingparts 39 a, 39 a, whereby the load can be prevented from beingconcentrated on the weld fixation parts 38 fixing the battery 8 and theelectrode tab 30 to each other, and the load exerted on the weldfixation parts 38 is moderated, whereby the weld fixation parts 38 canbe prevented from rupture or the like.

Here, as shown in FIG. 19, a nickel-made electrode tab 200 used in therelated art is formed with a welding slit 201 corresponding to aterminal surface of the battery cell 8, for spot welding to the terminalof the battery cell 8. In the electrode tab 200 in the related art, afirst welding electrode and a second welding electrode are operatedtwice in the manner of coming across the welding slit 201 to obtain atotal of four welding points; specifically, they are operated twice toobtain a total of four welding points, namely, weld fixation parts 38 a,38 b and weld fixation parts 38 c, 38 d, whereby the electrode tab 200is spot welded to the terminal surface of the battery cell 8. In thespot welding of the electrode tab 200 in the related art, thenon-effective shunt current, which flows from the first weldingelectrode directly to the second welding electrode through therelated-art electrode tab 200 instead of flowing through the weldingpoint and which therefore does not contribute to welding, is suppressedby elongating the non-effective shunt current path through providing thewelding slit 201. On the other hand, in the case of the electrode tab 30including a copper plate which is plated with nickel, copper has a verylow electrical resistivity, so that the magnitude of the non-effectiveshunt current is little changed even when the non-effective shuntcurrent path is elongated by providing the welding slit 201. In view ofthis, in the present invention, the electrode tab 30 is not providedwith a welding slit 201.

In addition, FIG. 20 is a diagram showing the distributions of weldstrength depending on the presence/absence of the welding slit 201 inthe electrode tab 30 including a nickel-plated copper plate, wherein thedistribution of weld strength in the case where the welding slit 201 isprovided is indicated by broken line H, while the distribution of weldstrength in the case where the welding slit 201 is not provided isindicated by solid line I. As shown in FIG. 20, the distribution of weldstrength is a normal distribution both when the welding slit 201 ispresent and when the welding slid 201 is absent. However, the mean valueof weld strength is about 85 N where the welding slit 201 is present,and is about 90 N where the welding slit 201 is absent, as in thepresent invention; thus, it was confirmed that the weld strength isenhanced by the absence of the welding slit 201. In view of this, theelectrode tab 30 is not provided with a welding slit 201 in the presentinvention.

As shown in FIG. 18, the electrode tab 30 not provided with any weldingslit 201 is provided with a position matching hole 37 for matching theposition thereof to the terminal of a battery cell 8 when the electrodetab 30 is spot welded to the terminal of the battery cell 8 by themanufacturer of the battery cell 8. The position matching hole 37 is athrough-hole which is formed to correspond substantially to the centerof the terminal face of the battery cell 8 when the electrode tab 30 isdisposed on the terminal of the battery cell 8, and which is formedsubstantially at the center in the width direction of the electrode tab30.

Thus, the position matching hole 37 is utilized as a register mark ofaligning it to a substantially central position of the terminal of thebattery cell 8 when the electrode tab 30 is disposed on the terminal ofthe battery cell 8 by the manufacturer who performs the spot welding,whereby the position matching between the center of the terminal of thebattery cell 8 and the position of the electrode tab 30 can be easilycarried out. In addition, the position matching hole 37 functions alsoas a register mark for applying the first welding electrode and thesecond electrode respectively to symmetric positions on the left andright sides of the substantially central position in the width directionof the electrode tab 30 when the electrode tab 30 is spot welded by themanufacturer.

In addition, in spot welding of the electrode tab 30, spot welding byuse of the first welding electrode and the second welding electrode inthe surroundings of the position matching hole 37 is conductedsymmetrically on the left and right sides of the position matching hole37, a total of two times, namely, once on the upper side (in FIG. 18)and once on the lower side, whereby the electrode tab 30 is welded tothe terminal of the battery cell 8 with four weld fixation parts 38 a to38 d. In this case, the position matching hole 37 and the weld fixationparts 38 a to 38 d are so laid out that the position matching hole 37 isprovided in a central area of the four corners of a substantiallyrectangular shape defined by the weld fixation parts 38 a to 38 d; forexample, they appear like the spots on a die indicating “5.” Therefore,the manufacturer can easily check, by visual inspection, whether weldinghas been conducted at all the necessary positions, without leaving anyyet-to-be-welded point.

Further, as shown in FIG. 21, each of the electrode tabs 30 has at leastone position matching hole 37 subjected to burring in which a tubularprojection is formed in the periphery of the hole by squeezingsimultaneously with boring at the time of press forming. The tubularprojection 37 a formed by the burring is formed, for example, at theposition matching hole 37 disposed on the most tip part 30 a side of theelectrode tab 30. Besides, the tubular projection 37 a is projected onthe side of the principal surface of the electrode tab 30 opposite tothe side of the principal surface to be brought into contact with thebattery cell 8. Therefore, with the position matching hole 37 of theelectrode tab 30 subjected to the burring, the tubular projection 37 ais formed at the principal surface part, whereby a plurality ofelectrode tabs 30 can be prevented from being stacked in secure contactwith each other, and the manufacturer can be prevented from unknowinglypicking up a plurality of electrode tabs 30 at a time.

As shown in FIG. 22, a lower case 4 for containing the battery cells 8partitioned by the partition member 20 is formed in a roughlyrectangular box-like shape having an opening part on the upper side. Inaddition, the lower case 4 is formed with a terminal part 6 at a lowerpart of the front surface 2 b. As shown in FIG. 23, the terminal part 6includes: terminal holes 41 exposed from the front surface 2 b to theexterior; and a terminal case 40 in which joint members 70 disposed onthe inner side of the terminal holes 41 and receiving terminal pins (notshown) formed on the battery mount part 5 side and inserted therein isfitted.

As shown in FIG. 23, the terminal hole 41 includes: a recessed surfacepart 42 formed at the front surface 2 b of the casing 2; and a guidepart 43 formed at the recessed surface part 42 to be continuous with thejoint member 70. The recessed surface part 42 formed at the frontsurface 2 b of the casing 2 is a roughly rectangular recess, whichprevents a short-circuit from occurring due to contact of the jointmember 70 with external metals and prevents the joint member 70 frombeing deformed by collision on an external body. The recessed surfacepart 42 is provided with a guide part 43 opened in a substantiallycircular shape roughly in the center of the bottom surface thereof. Theguide part 43 formed at the recessed surface part 42 includes: a supportsurface part 44 formed to be substantially equal in diameter to thejoint member 70 and operative to support the terminal pin together withthe joint member 70; and an inclined surface part 45 opened, with adiameter greater than the diameter of the terminal pin, on the recessedsurface part 42 side of the support surface part 44 and operative toguide the terminal pin into the joint member 70. The inclined surfacepart 45 formed on the recessed surface part 42 side of the supportsurface part 44 is opened with a diameter greater than the diameter ofthe terminal pin, so that it permits the terminal pin to be easilyinserted into the support surface part 44. The support surface part 44into which the terminal pin guided by the inclined surface part 45 isinserted is formed to be substantially equal in diameter to the jointmember 70 and be continuous with the joint member 70, and thereforeensures that the terminal pin guided by the inclined surface part 45 canbe inserted into the joint member 70 without any load exerted thereon.In addition, the support surface part 44 holds the terminal pin,together with the joint member 70.

As shown in FIG. 24, the terminal case 40 disposed inside the terminalhole 41 is a roughly rectangular resin part formed to have major edgessubstantially equal in length with the inside width of the lower case 4.The terminal case 40 is provided along its major edge direction withfitting holes 46 in which to contain the joint members 70, and the maincircuit board 50 is attached to the terminal case 40.

As shown in FIG. 9, the main circuit board 50 attached to the terminalcase 40 is a printed wiring board having conductor patterns formed onone side, on both sides, or in multiple layers, and is a rigid board. Inaddition, the main circuit board 50 is formed to be roughly the same insize and shape as the inside of the lower case 4. Besides, as shown inFIG. 25B, the main circuit board 50 is provided, in the vicinity of theone-side minor edge to be attached to the terminal case 40 of theprimary surface on the back surface side, with first to fifth terminalconnection parts 53 a to 53 e (hereinafter, the first to fifth terminalconnection parts 53 a to 53 e will also be referred to simply as theterminal connection parts 53) to be connected to the joint members 70through connection tabs 71, correspondingly to the layout positions ofthe first to five terminal parts 6 a to 6 e.

As shown in FIG. 23, the joint member 70 contained in the terminal case40 is a metallic member which is disposed to be continuous with thesupport surface part 44 of the terminal hole 41 and which has acylindrical shape opened at one end of the longitudinal direction andclosed at the other end. The fitting hole 46 in which to contain thejoint member 70 has a cylindrical shape having an inner diametersubstantially equal to the outer diameter of the joint member 70 andbeing opened at both ends of the longitudinal direction. The jointmembers 70 are fitted in the fitting holes 46, and are continuous withthe terminal holes 41 through the end faces of the fitting holes 46 onthe open end side thereof. On the closed end side, the joint members 70are fixed by welding or soldering to the metal-made connection tabs 71soldered respectively to the terminal connection parts 53 a to 53 e ofthe main circuit board 50 attached to the terminal case 40 (see FIG.25B). Since the terminal case 40 is disposed inside the lower case 4together with the main circuit board 50, as shown in FIG. 23, the jointmembers 70 are continuous with the support surface parts 44 of theterminal holes 41, and support the terminal pins inserted in the supportsurface parts 44 in the inserted state.

In the terminal part 6 as above, the insertion holes are opened insidethe recessed surface parts 42 of the terminal holes 41, and continuationthereof with the joint members 70 through the guide parts 43 is secured,whereby the joint members 70 are disposed on the inner side of thecasing 2 relative to the front surface 2 b. This ensures that theterminal part 6 can prevent a short-circuit from occurring between thejoint members 70 and external metals and can prevent the joint membersfrom deformation or the like due to collision on an external body. Inthe terminal part 6, besides, the terminal pins are inserted and held inboth the support surface parts 44 of the guide parts 43 of the terminalholes 41 and the joint members 70 fitted in the terminal case 40. Thus,the terminal pins are each inserted and held in two component parts,namely, the terminal hole 41 on the lower case 4 side and the terminalcase 40 disposed inside the lower case 4. This ensures that, even when avibration is exerted on the electronic apparatus at the time of loadingthe battery pack 1, the load exerted on the terminal pins can belessened, and reliability of electrical connection can be maintained.

Besides, as shown in FIG. 4, in the terminal part 6 as above, fiveterminal parts, namely, the first to fifth terminal parts 6 a to 6 e aredisposed side by side at a lower part of the front surface 2 b. Thefirst and second terminal parts 6 a, 6 b and the fourth and fifthterminal parts 6 d, 6 e are formed at left-right symmetrical positionsin the front surface 2 b of the casing 2. The third terminal part 6 c isformed at a position deviated from the center of the front surface 2 btoward the side of the fourth and fifth terminal parts 6 d, 6 e. Inaddition, an end face of the insertion guide groove 11 is exposed at thecenter of the front surface 2 b.

Besides, as above-mentioned, the terminals formed at the terminal parts6 a to 6 e have respective functions assigned according to the SMBusinterface standard. Specifically, the first terminal part 6 a has thefunction of a positive electrode terminal of the battery pack 1, thesecond terminal part 6 b has the function of a clock line terminal, thethird terminal part 6 c has the function of a data line terminal, thefourth terminal part 6 d has the function of an ID terminal to which anID resistor is connected, and the fifth terminal part 6 e has thefunction of a negative electrode terminal of the battery pack 1.

In use of the battery pack 1, the casing 2 is inserted into the batterymount part 5, and is slid toward the front surface 2 b side, whereby theterminal pins disposed on the battery mount part 5 side are insertedinto and held in the terminal parts 6 a to 6 e, respectively. Here, acommunication circuit unit 57 for performing communication with anexternal electronic apparatus or the like connected to the terminalparts 6 a to 6 e is mounted on the main circuit board 5, by use of aplurality of electronic parts such as IC chips. Consequently, as shownin FIG. 10, the battery pack 1 enables various operations between thecommunication circuit unit 57 on the main circuit board 50 and theelectronic apparatus side, such as supply of electric power through thefirst and fifth terminal parts 6 a, 6 e, communication of various data,for example, residual battery charge, full charge, the current charge,the time for which the battery pack 1 can be used under the currentconditions, or the number of charge-discharge cycles, ID data indicativeof the battery pack 1 being a genuine product, etc. through the thirdterminal part 6 c, and detection of the ID resistance through the fourthterminal part 6 d, according to clock data supplied through the secondterminal part 6 b.

The ID resistance detected through the fourth terminal part 6 d is usedto detect, on the electronic apparatus side, which one of a plurality oftypes of battery packs prepared according to the different values ofcapacity has been loaded; in short, different resistance values are setrespectively for the L-size battery pack 1 and the S-size battery pack100. When a terminal pin is inserted into the fourth terminal part 6 d,the resistance on the side of the battery pack 1, 100 is measured on theelectronic apparatus side, and it is decided which one of the batterypacks 1 and 100 has been loaded.

Here, the fourth terminal part 6 d is formed in proximity to the fifthterminal part 6 e having the function of the negative electrodeterminal. The reason is as follows. If the ID detection resistor and thenegative electrode line are disposed remote from each other,electromagnetic radiations from the other signal lines and the like maybe propagated therebetween as noises, possibly making it hard to achieveaccurate measurement of resistance. In the battery pack 1, therefore,the fourth terminal part 6 d is disposed in proximity to the negativeelectrode terminal constituted of the fifth terminal part 6 e, whichmakes it possible to design a short distance between the ID resistor andthe negative electrode line, and to achieve accurate measurement ofresistance.

In addition, in consideration of the structure in which the insertionguide groove 11 on the front surface side is formed substantially at thecenter in the width direction of the front surface 2 b of the casing 2,the third terminal part 6 c is formed at a position deviated to eitherof the left and right sides, in this embodiment, to the side of thefourth and fifth terminal parts 6 d, 6 e.

As a result, the battery pack 1 has a configuration in which theterminal parts 6 a to 6 e are disposed at nonuniform intervals, and,accordingly, the terminal pins formed on the battery mount part 5 sideare also formed at nonuniform intervals corresponding to the terminalparts 6 a to 6 e, respectively. Therefore, the terminal pins may not beinserted into the terminal parts 6 a to 6 e when the left and rightsides of the battery pack 1 are reversed (in relation to those in thecorrect insertion mode), so that mis-insertion of the battery pack 1into the battery mount part 5 can be obviated.

Besides, as shown in FIGS. 25A and 25B, between the second terminal part6 b and the third terminal part 6 c and between the third terminal part6 c and the fourth terminal part 6 d, the first and fifth electrode tabs31, connected to the electrodes of the battery cell 8 are disposed insuch a manner as to overlap with neither of the third and fourthterminal parts 6 c, 6 d. The first and fifth electrode tabs 31, 35electrically connected between the terminals of the battery cell 8 areformed to be narrower on the side of their tip parts 31 a, 35 a, andwhen they are contained into the casing 2, the tip parts 31 a, 35 a arebent and then soldered respectively to first and fifth electrode tabconnection parts 52 a, 52 e of the main circuit board 50. With thebattery cell 8 contained in the casing 2 together with the main circuitboard 5, the first and fifth electrode tabs 31, 35 are so disposed thattheir tip parts 31 a, 35 a are located between the second terminal part6 b and the third terminal part 6 c and between the third terminal part6 c and the fourth terminal part 6 d, but not located on the same planeas the terminal parts 6 a to 6 e. In addition, the first and fifthelectrode tabs 31, 35 are bent from end parts of the battery cell 8along the main circuit board 50, whereby their narrowed tip parts 31 a,35 a are so laid around as not to overlap with the second to fourthterminal parts 6 b to 6 d. Therefore, in the battery pack 1,electromagnetic radiations due to the first and fifth electrode tabs 31,35 can be prevented from being propagated as noises to communicationlines, and accurate data communication can be achieved.

In addition, as shown in FIGS. 22 and 24, the main circuit board 50 isattached to the principal surface, on the opposite side of the principalsurface brought into contact with the terminal holes 41, of the terminalcase 40. As shown in FIGS. 26 and 27, the principal surface, on theopposite side of the principal surface brought into contact with theterminal holes 41, of the terminal case 40 is provided with boardsupport parts 47 for clamping one minor edge of the main circuit board50 in the thickness direction of the main circuit board 50. The boardsupport part 47 includes a lower side support part 47 a for supportingone principal surface of the main circuit board 50, and an upper sidesupport part 47 b for supporting the other principal surface of the maincircuit board 50. The lower side support parts 47 a are projectinglyprovided in plurality between both end parts in the major edge directionof the terminal case 40 and the fitting holes 46. In addition, in thevicinity of a substantially central position of the minor edge on oneside of the main circuit board 50, a lower side support part 47 csupporting the one-side principal surface of the main circuit board 50in the same manner as the lower side support part 47 a but projectedlargely as compared with the lower side support part 47 a is provided.The upper side support parts 47 b are projectingly provided near bothends in the width direction of the main circuit board 50, in the stateof being spaced from the lower side support parts 47 a, 47 c by anamount roughly equivalent to the thickness of the main circuit board 50.Thus, the principal surfaces on one side and the other side of the maincircuit board 50 are supported respectively by the lower side supportparts 47 a, 47 c and the upper side support part 47 b of the boardsupport parts 47, whereby the main circuit board 50 is mounted to theterminal case 40.

As shown in FIG. 28, the main circuit board 50 disposed inside the lowercase 4 together with the terminal case 40 is mounted while beingsupported by the board support parts 47, so that the main circuit board50 is provided in the state of being spaced from the inside bottomsurface of the lower case 4. This ensures that electronic parts largerin height than existing ones can also be mounted on the principalsurface, facing the bottom surface of the lower case 4, of the maincircuit board 50.

Further, the main circuit board 50 is provided with rib relief grooves54 corresponding to the layout positions of case reinforcing ribs 4 aformed in the inside of the lower case 4. The rib relief grooves 54 areformed to leave clearances between themselves and the case reinforcingribs 4 a, so that the main circuit board 50 is prevented frominterfering with the case reinforcing ribs 4 a.

Here, the partition member 20 disposed over the main circuit board 50 issupported by a support part 48 formed at the upper surface of theterminal vase 40 shown in FIG. 24 and by support protrusions 4 b formedinside the lower case 4 shown in FIG. 24. The support part 48 formed atthe upper surface of the terminal case 40 has a groove shape opened onthe upper side, and a support piece 21 a provided on the lower side ofthe front surface of the partition plate 21 of the partition member 20as shown in FIGS. 9, 11A and 11B is inserted in the support part 48,whereby the partition member 20 is supported. As shown in FIG. 24, thesupport protrusions 4 b formed inside the lower case 4 are projectinglyprovided on the lower surface near the back surface of the lower case 4,at substantially symmetric positions on the left and right sides of thecenter in the width direction of the lower case 4, and are formed to becontinuous with the tips of the case reinforcing ribs 4 a of the lowercase 4. As shown in FIG. 28, the support protrusions 4 b are abutted onthe positioning plate 22 of the partition member 20, thereby supportingthe partition member 20. Therefore, the partition member 20 is stablysupported at three or more points, since the support piece 21 a issupported by the support part 48 while the positioning plate 22 issupported by the plurality of support protrusions 4 b.

On the other hand, as shown in FIGS. 24 and 28, the main circuit board50 is provided with support protrusion passing holes 55 through which topass the support protrusions 4 b, correspondingly to the layoutpositions of the support protrusions 4 b. The support protrusion passingholes 55 are formed to be larger in diameter than the supportprotrusions 4 b, which prevents the main circuit board 50 frominterfering with the support protrusions 4 b. This ensures that the maincircuit board 50 is provided inside the lower case 4 in the state ofbeing supported by the terminal case 40 in a cantilever mode, withoutinterfering with the lower case 4. With the main circuit board 50 thusconfigured, therefore, for example when the battery pack 1 or 100 isdropped or in the like occasion, the impact load generated due to thedropping of the battery pack, the battery pack 1 or 100 can be preventedfrom being exerted on the main circuit board 50 through the lower case4. Further, the load of the battery cell 8 disposed over the maincircuit board 50 can be prevented from being exerted on the main circuitboard 50.

In addition, as shown in FIG. 1, the lower case 4 for containing theterminal case 40 and the main circuit board 50 as above is provided inits lower surface 2 a with a pair of insertion guide grooves 11, 12which extend in the direction of sliding between the mount position ofthe battery mount part 5 and the loading/unloading position and whichare spaced from each other along the sliding direction. Guideprojections (not shown) projectingly provided at the bottom surface ofthe battery mount part 5 are inserted into the insertion guide grooves11, 12, whereby the loading/unloading operations of the casing 2 can beguided, and the casing 2 mounted in the battery mount part 5 can beprevented from chattering in the directions of both side surfaces 2 c, 2d.

Further, as shown in FIG. 1, the lower case 4 is provided with adetection recess or recesses 13 for detection of the species of thebattery pack 1, at either one or both of edges formed by the lowersurface 2 a and both side surfaces 2 c, 2 d. The detection recesses 13are provided at both side surfaces 2 c, 2 d in the case of the L-sizebattery pack 1, and the detection recess 13 is provided only on the sideof the other side surface 2 d in the case of the S-size battery pack100. This ensures that, in using the battery pack 1, the species such asL-size and S-size of the battery packs 1, 100 can be detected, bymis-insertion preventive engaging projections (not shown) projectinglyprovided at side surfaces, facing both side surfaces 2 c and 2 d of thecasing 2, of the battery mount part 5 correspondingly to the detectionrecesses 13.

In addition, the lower case 4 is provided with locking recesses 14 and15 at positions which are on the edges formed by the lower surface 2 aand the side surfaces 2 c, 2 d and which are on both sides of thedetection recess 13. When the casing 2 is inserted into the batterymount part 5 and slid to the mount position, the locking recesses 14 and15 are locked on locking projections (not shown) projectingly providedat side surfaces of the battery mount part 5 correspondingly to thelocking recesses 14, 15, whereby the battery pack 1 is mounted to thebottom surface of the battery mount part 5.

Furthermore, the lower case 4 is welded to the upper cover 3 in thestate of covering the battery cell 8 contained therein. The upper cover3 is formed by use of a synthetic resin. As shown in FIGS. 1B and 3B,one side surface 2 c, which is adjacent to the front surface 2 b and theback surface 2 e and which is directed vertically up when the batterypack 1 is mounted into the battery mount part 5, of the casing 2 isprovided with an identification part 9 a for identification of thegripping surfaces according to the mounting direction. Furthermore, thefront surface 2 b and the back surface 2 e of the casing 2 are providedwith anti-slip parts 9 b at the positions of gripping by the user.

The identification part 9 a formed on the one side surface 2 c which isdirected up when the battery pack 1 is mounted into the battery mountpart 5 is for permitting the user to identify the gripping surfaces ofthe casing 2 at the time of mounting the battery pack 1 into the batterymount part 5. The identification part 9 a is formed by forming arecessed surface part in the one side surface 2 c, graining the insideof the recessed surface part and, further, graining the recessed surfacepart to form projected lines extending in the front-rear direction. Thispermits the user, when gripping the battery pack 1 by his right hand, toput the index finger or the middle finger on the one side surface 2 c,causing the identification part 9 a to make contact with the fingertip,thereby intuitively recognize that the battery pack 1 is being correctlygripped with the one side surface of the casing 2 directed up, andintuitively sensing the sliding direction upon insertion of the casing 2in the battery mount part 5. Accordingly, mis-insertion of the batterypack 1 can be prevented.

The anti-slip parts 9 b formed in the front surface 2 b and the backsurface 2 e are provided for permitting the user to easily grip thecasing 2 and for preventing slip-off of the casing 2 at the time ofmounting the battery pack 1 into the battery mount part 5, inconsideration of the fact that the battery pack 1 for use inbusiness-use electronic apparatuses contains more battery cells 8 and ishence heavier as compared with the battery pack for use in private-useelectronic apparatuses. The anti-slip parts 9 b are formed by formingrecessed surface parts at upper parts of the front surface 2 b and theback surface 2 e, and graining the inside of the recessed surface parts.

With the identification part 9 a and the anti-slip parts 9 b thusformed, the battery pack 1 permits the user to see that the casing 2 isbeing gripped correctly for mounting it into the battery mount part 5,to avoid mis-insertion of the battery pack 1, and to securely recognizean increase, if any, in the weight of the casing 2.

Incidentally, the casing 2 is not only grained at the identificationpart 9 a and the anti-slip parts 9 b of the upper cover 3 but alsograined in other regions in a manner different from the identificationpart 9 a and the anti-slip parts 9 b.

In addition, in consideration of the use for such electronic apparatusesas the business-use video camera 7, the casing 2 including the lowercase 4 and the upper cover 3 has a configuration in which the lower case4 and the upper cover 3 are greater in material thickness than thepartition member 20.

The casing 2 in the related art is formed in a minimum materialthickness which promises a reduced size instead of a larger outer sizeand which conforms to the UL (Underwriters Laboratories Inc.) 94Standard (fire retardancy of plastics). Therefore, in the battery packsaccording to the related art, the material thickness of the partitionmember 20 is set to be larger than that of the casing 2, and enhancementof the impact resistance of the partition member 20 for partitioning thebattery cells 8 contained in the casing 2 is contrived, so as to enhancethe overall impact resistance performance.

However, the battery pack 1 to be used in such electronic apparatuses asvideo camera 7 for business use contains more battery cells 8 and ishence heavier, as compared with the battery pack to be used inprivate-use electronic apparatuses, so that the casing 2 itself exposedto the exterior is more keenly requisite to have a high strength.

For example, as shown in FIGS. 29A, 29B and 29C, the upper cover 3 isformed by adopting the material thickness values of 1.5 mm (t1) for theupper surface 2 f, 1.5 mm (t2) for the front surface 2 b, 1.5 mm (t3)for the one side surface 2 c, 1.5 mm (t4) for the other side surface 2d, and 1.5 mm (t5) for the back surface 2 e. In addition, as shown inFIGS. 30A, 30B and 30C, the lower case 4 is formed by adopting thematerial thickness values of 1.8 mm (t6) for the lower surface 2 a, 1.5mm (t7) for the front surface 2 b, 1.5 mm (t8) for the one side surface2 c, 1.5 mm (t9) for the other side surface 2 d, and 1.5 mm (t10) forthe back surface 2 e. Further, as shown in FIGS. 29B and 29C, the uppercover 3 has a configuration in which the front surface 2 b, the one sidesurface 2 c, the other side surface 2 d and the back surface 2 e areprovided respectively with pluralities of cover reinforcing ribs 3 b;similarly, the lower case 4 is also provided with pluralities of casereinforcing ribs 4 a. Besides, as shown in FIGS. 11 and 31, thepartition member 20 is formed by adopting the material thickness valuesof 1 mm (t11) for the partition plate 21, 0.8 mm (t12) for thepositioning plate 22, 0.8 mm (t13) for the attaching plate 23, 0.8 mm(t14) for the support plates 24, and 1 mm (t15) for the reinforcing ribs25. In short, the casing 2 including the upper cover 3 and the lowercase 4 is formed by adopting material thickness values of about 1.5 to1.8 mm, whereas the partition member 20 is formed by adopting materialthickness values of about 0.8 to 1 mm.

Therefore, when the battery pack 1 has a configuration in which thematerial thickness of the partition member 20 conforms to the UL 94Standard, the casing 2 is set to be thinner and the casing 2 is set tobe thicker, it is possible, for example while using the same overallamount of resin material as in the related art, to enhance the strengthof the casing 2 and to enhance the impact strength performance. Inaddition, when the battery pack 1 has a configuration in which thematerial thickness of the partition member 20 contained in the casing 2is set smaller, a reduction in the overall size of the casing 2 can bepromised.

In addition, end parts of the upper cover 3 and the lower case 4 areopposed to and abutted on each other, and are welded to each other byultrasonic welding. Here, FIG. 32 is an essential part enlarged view ofpart J of FIG. 29B and part K of FIG. 30B, showing the condition whereend parts of the upper cover 3 and the lower case 4 are opposed to andabutted on each other. As shown in FIG. 32, the lower case 4 is formedwith a first welding projection 4 c along the whole inside periphery ofthe end part to be welded to the upper cover 3, and with a first weldingrecess 4 d along the whole outside periphery of the end part. On theother hand, the upper cover 3 is formed with a second welding recess 3 cto be engaged with the first welding projection 4 c, along the wholeinside periphery of the end part to be welded to the lower case 4, andwith a second welding projection 3 d to be engaged with the firstwelding recess 4 d, along the whole outside periphery of the end part.

This ensures that, when the end parts of the upper cover 3 and the lowercase 4 are opposed to and abutted on each other, the first weldingprojection 4 c of the lower case 4 is engaged with the second weldingrecess 3 c of the upper cover 3, and the second welding projection 3 dof the upper cover 3 is engaged with the first welding recess 4 d of thelower case 4, so that position matching can be easily achieved, thewelding area of the upper cover 3 and the lower case 4 is enlarged, andan enhanced weld strength between the upper cover 3 and the lower case 4is promised. Therefore, the upper cover 3 and the lower case 4 can beenhanced in impact resistance against an impact load generated, forexample, in a situation in which the battery pack 1 to be used in suchelectronic apparatuses as the video camera 7 for business use thatcontains more battery cells 8 and is hence heavier as compared with thebattery pack to be used in private-use electronic apparatuses is droppedor the like situation.

In addition, the first welding projection 4 c and the first weldingrecess 4 d of the lower case 4 are formed with rough surfaces. Thisensures that, in welding the lower case 4 and the upper cover 3 to eachother, the lower case 4 formed with the rough surface is more liable togenerate frictional heat at the surface of welding to the upper cover 3,as compared with the related art. As a result, the surface of welding tothe upper cover 3 is melted more easily, weldability of the surface tothe upper cover 3 is enhanced, and ultrasonic welding is thusfacilitated, as compared with the related art.

Incidentally, the lower case 4 is not limited to the configuration inwhich the first welding projection 4 c and the first welding recess 4 dare formed with rough surfaces, and it suffices that either one of thefirst welding projection 4 c and the first welding recess 4 d is formedwith a rough surface, insofar as ultrasonic welding of the upper cover 3and the lower case 4 can be achieved easily. Besides, the configurationin which the first welding projection 4 c and/or the first weldingrecess 4 d of the lower case 4 is formed with a rough surface is notlimitative, and a configuration may be adopted in which the secondwelding projection 3 d and/or the second welding recess 3 c of the uppercover 3 is formed with a rough surface. Furthermore, a configuration maybe adopted in which the first welding projection 4 c and/or the firstwelding recess 4 d and the second welding projection 3 d and/or thesecond welding recess 3 c are formed with rough surfaces.

Now, the S-size battery pack 100 in which four battery cells 8 i to 8 lare contained in two rows and two layers will be described. In thefollowing description of the S-size battery pack 100, the parts havingconfigurations the same as or equivalent to those in the L-size batterypack 1 described above will be denoted by the same reference symbols asused above, and descriptions of them will be omitted.

As shown in FIG. 33, the battery cells 8 i to 8 l contained in two rowsand two layers in a casing 2 of the S-size battery pack 100 arecylindrical lithium ion secondary cells (hereinafter, the battery cells8 i to 8 l will also be referred to simply as the battery cells 8). Thebattery cells 8 are arranged in two rows and two layers so that theirmajor axes are substantially parallel to the major edges of a maincircuit board 50. Specifically, as shown in FIGS. 34A, 34B and 35, ofthe battery cells 8, the first battery cell 8 i is disposed in thevicinity of a first terminal connection part 53 a (see FIG. 25B) whichis electrically connected to a first terminal part 6 a and which isdisposed on one side in the width direction of the main circuit board50, and the second battery 8 j is disposed on the first battery cell 8i. In addition, of the battery cells 8, the third battery cell 8 k isdisposed in the vicinity of a fifth terminal connection part 53 e (seeFIG. 25B) which is electrically connected to a fifth terminal part 6 eand which is disposed on the other side in the width direction of themain circuit board 50, and the fourth battery cell 8 l is disposed onthe third battery cell 8 k.

Further, the first battery cell 8 i and the fourth battery cell 8 l areso disposed that their positive electrode terminals 10 a front on theside of the terminal parts 6, namely, on the side of a front surface 2b. In addition, the second battery cell 8 j and the third battery cell 8k are so disposed that their negative electrode terminals 10 b front onthe side of the terminal parts 6, namely, on the side of the frontsurface 2 b.

In the case where the battery pack 100 is to be used in electronicapparatuses for business use, the battery cells 8 arranged in two rowsand two layers as above have to be all (four of them) connected inseries, since the battery pack 100 needs a rated voltage of about 14.4 Vand each of the battery cells 8 has a rated voltage of about 3.6 V.Taking this into account, the terminals of the battery cells 8 in thestate of being partitioned by a partition member 20 are connectedthrough electrode tabs 80, whereby the four battery cells 8 areconnected in series.

Specifically, as shown in FIG. 35, the positive electrode terminal 10 aof the first battery cell 8 i disposed in the row on one side and afirst electrode tab connection part 52 a of the main circuit board 50are electrically connected to each other through the first electrode tab81. The first electrode tab 81 is fixed to the terminal by spot welding,and its tip part 81 a is bent and soldered to the first electrode tabconnection part 52 a.

Further, of the battery cells 8, the negative electrode terminal 10 b ofthe first battery cell 8 i disposed in the row on one side and thepositive electrode terminal 10 a of the second battery cell 8 j areelectrically connected to each other through a second electrode tab 82.The second electrode tab 82 is fixed to the terminals by spot welding,and its tip part 82 a is bent and soldered to a second electrode tabconnection part 52 b.

In addition, of the battery cells 8, the positive electrode terminal 10b of the second battery cell 8 j disposed in the row on one side and thepositive electrode terminal 10 a of the fourth battery cell 8 l disposedin the row on the other side are electrically connected to each otherthrough a third electrode tab 83. The third electrode tab 83 is fixed tothe terminals by spot welding.

Further, of the battery cells 8, the positive electrode terminal 10 a ofthe third battery cell 8 k disposed in the row on the other side and thenegative electrode terminal 10 b of the fourth battery cell 8 l areelectrically connected to each other through a fourth electrode tab 84.The fourth electrode tab 84 is fixed to the terminals by spot welding,and its tip part 34 a is bent and soldered to a fourth electrodeterminal connection part 52 d of the main circuit board 50.

Besides, of the battery cells 8, the negative electrode terminal 10 b ofthe third battery cell 8 k disposed in the row on the other side and afifth electrode tab connection part 52 e of the main circuit board 50are electrically connected to each other through a fifth electrode tab85. The fifth electrode tab 85 is fixed to the terminal by spot welding,and its tip part 85 a is bent and soldered to the fifth electrode tabconnection part 52 e (hereinafter, the first to fifth electrode tabs 81to 85 will also be referred to simply as the electrode tabs 80).

As shown in FIG. 36, the four battery cells 8 arranged in two rows andtwo layers as above-described, namely, the first battery cell 8 i, thesecond battery cell 8 j, the fourth battery cell 8 l and the thirdbattery cell 8 k in this order are connected in series through theelectrode tabs 80.

Thus, in the battery pack 100 configured as above, the battery cells 8each having a rated voltage of about 3.6 V are arranged in two rows andtwo layers over the main circuit board 50, and the four battery cells 8are connected in series to realize an overall rated voltage of about14.4 V. Therefore, the battery pack 100 can be used in business-useelectronic apparatuses such as the video camera 7.

In addition, as shown in FIGS. 34A and 34B, the partition member 20 isfitted with a display circuit board 60 on the upper side of the secondbattery cell 8 j and the fourth battery cell 8 l. The display circuitboard 60 is electrically connected to a board connection tab part 83 aformed at a substantially middle position of the third electrode tab 83.The board connection tab part 83 a is bent relative to the thirdelectrode tab 83, and is soldered to a board connection part 63 of thedisplay circuit board 60. Further, the display circuit board 60 iselectrically connected to the main circuit board 50 through a flexibleflat cable 36. The flexible flat cable 36 is fixed at its one end to acable connection part 64 of the display circuit board 60, and iselectrically connected at its other end to the third electrode tabconnection part 52 c of the main circuit board 50. This permits thethird electrode tab 83 to be electrically connected to the main circuitboard 50 through the display circuit board 60, without needingcomplicated wiring or the like.

Thus, in the battery pack 100, as shown in FIG. 36, the first to fifthelectrode tabs 81 to 85 are electrically connected to the main circuitboard 50 through the first to fifth electrode tab connection parts 52 ato 52 e, respectively. Therefore, the voltages across the fourrespective battery cells 8 connected in series can be detected by avoltage detection unit 56 of the main circuit board 50, so that theresidual battery charges of the battery cells 8, the presence/absence ofan abnormality in the battery cells 8, etc. can be checked.

The partition member 20 for partitioning these battery cells 8 includes:a roughly rectangular sheet-like partition plate 21; a positioning plate22 which is formed at one side surface of the partition plate 21 so asto be substantially orthogonal to the principal surfaces of thepartition plate 21 and to which the main circuit board 50 is attached;an attaching plate 23 which is formed at the other side surface of thepartition plate 21 on the opposite side of the positioning plate 22 andto which the display circuit board 60 is attached; support plates 24 g,24 h (hereinafter, the support plates 24 g and 24 h will also bereferred to simply as the support plates 24) which are formed atsubstantially regular intervals between the positioning plate 22 and theattaching plate 23 and which partition each of the rows of the batterycells 8; and reinforcing ribs 25 formed respectively in the cornersformed by the partition plate 21 and the support plates 24.

The partition plate 21 has the principal surfaces, each of which theminor edges where the positioning plate 22 and the attaching plate 23are formed have a length approximately equal to the overall length ofthe battery cell, and the major edges have a length approximately equalto the overall height of the battery cells 8 stacked in two layers. Thepartition plate 21 having such principal surfaces is disposed betweenthe one-side row of the battery cells 8 arranged in two rows and twolayers, specifically, the row including the first and second batterycells 8 i, 8 j, and the other-side row of the battery cells 8,specifically, the row including the third and fourth battery cells 8 k,8 l, thereby partitioning the battery cells 8 i, 8 j in the one-side rowfrom the battery cells 8 k, 8 l in the other-side row.

In addition, the positioning plate 22, the attaching plate 23 and thedisplay circuit board 60 are configured in the same manner asabove-described, and, hence, descriptions of them are omitted.

The support plates 24 provided between the positioning plate 22 and theattaching plate 23, in a total number of two, are provided respectivelyon the principal surfaces of the partition plate 21, as shown in FIG.35. Specifically, on each principal surface of the partition plate 21,the support plate 24 is disposed so as to be substantially parallel tothe positioning plate 22 and the attaching plate 23, namely, to besubstantially orthogonal to the principal surface of the partition plate21, and to provide substantially regular intervals (which areapproximately equal to the diameter of the battery cell 8) along themajor edge direction (height direction) of the partition plate 21.

To be more specific, the first support plate 24 g is formed on theprincipal surface on one side of the partition plate 21, and the secondsupport plate 24 h is formed on the principal surface on the other sideof the partition plate 21. The first partition plate 24 g partitions thefirst battery cell 8 i and the second battery cell 8 j from each other.The second support plate 24 h partitions the third battery cell 8 k andthe fourth battery cell 8 l from each other. In other words, the firstbattery cell 8 i is disposed between the first support plate 24 g andthe positioning plate 22, the second battery cell 8 j is disposedbetween the first support plate 24 g and the attaching plate 23, thethird battery cell 8 k is disposed between the second support plate 24 hand the positioning plate 22, and the fourth battery cell 8 l isdisposed between the second support plate 24 h and the attaching plate23.

In addition, as shown in FIGS. 34A and 34B, of the battery cells 8arranged in two rows and two layers, partitioned by the partition member20 and having their terminals electrically connected through theelectrode tabs 80, the second battery 8 j disposed in the one-side rowand the fourth battery cell 8 l disposed in the other-side row areconnected through the third electrode tab 83 in the manner of bridgingbetween the one-side row and the other-side row. On the other hand, thefirst battery cell 8 i disposed in the one-side row and the thirdbattery cell 8 k disposed in the other-side row are not connectedthrough the first, second, fourth and fifth electrode tabs 81, 82, 84,85 in the manner of bridging between the one-side row and the other-siderow, either on the side of the front surface 2 b or on the side of theback surface 2 e.

Further, referring to the first and second battery cells 8 i, 8 j, thenegative electrode terminal 10 b of the first battery cell 8 i and thepositive electrode terminal 10 a of the second battery cell 8 j areconnected to each other by the second electrode tab 82 on the backsurface 2 e side. Similarly, referring to the third and fourth batterycells 8 k, 8 l, the positive electrode terminal 10 a of the thirdbattery cell 8 k and the negative electrode terminal 10 b of the fourthbattery cell 8 l are connected to each other by the fourth electrode tab84 on the back surface 2 e side. In the case where for example thebattery pack is handled by the manufacturer, the first battery cell 8 imay be turned in the direction of arrow L1 in FIG. 34A, with the secondelectrode tab 82 as a center, in such a manner that the positiveelectrode terminal 10 a side of the first battery 8 i would be loosenedand released from the partition member 20. Similarly, the third batterycell 8 k may be turned in the direction of arrow L2 in FIG. 34A, withthe fourth electrode tab 84 as a center, in such a manner that thenegative electrode terminal 10 b side of the third battery cell 8 kwould be loosened and released from the partition member 20.

In order to obviate such a trouble, the first battery 8 i and the thirdbattery cell 8 k are supported by the support plates 24 so that theywould not be loosened and released from the partition member 20. Thefirst support plate 24 g is provided with a first projected piece (notshown) for supporting the first battery cell 8 i, and the second supportplate 24 h is provided with a second projected piece 28 f for supportingthe second battery cell 8 j (hereinafter, the first projected piece (notshown) and second projected piece 28 f will also be referred to simplyas the projected pieces 28).

The first projected piece 28 (not shown) cooperates with the positioningplate 22 adjacent thereto in the height direction in clampinglysupporting therebetween the first battery cell 8 i disposed between thefirst projected piece (not shown) and the positioning plate 22. Thesecond projected piece 28 f cooperates with the positioning plate 22adjacent thereto in the height direction in clampingly supportingtherebetween the third battery cell 8 k disposed between the secondprojected piece 28 f and the positioning plate 22. In other words, thefirst battery cell 8 i is supported by being clamped between the firstprojected piece (not shown) and the positioning plate 22, and the thirdbattery cell 8 k is supported by being clamped between the secondprojected piece 28 f and the positioning plate 22.

This ensures that, with the first battery cell 8 i and the third batterycell 8 k supported by the support plates 24, the projected pieces 28 canprevent the first battery cell 8 i and the third battery cell 8 k (whichare not connected by the electrode tabs 80 in the manner of bridgingbetween the one-side row and the other-side row) from being loosened andreleased from the support plates 24.

Reinforcing ribs 25, the electrode tabs 80, a lower case 4, and an uppercover 3 are configured in the same manner as in the above-describedbattery pack 1, and, therefore, descriptions of them are omitted.

In the battery pack 1 configured as above-described, the battery cells 8each having a rated voltage of about 3.6 V are arranged in two rows andfour layers, the battery cells 8 in each set of paired battery cells areconnected in parallel, and the four sets of the parallel-connectedpaired battery cells 8 are sequentially connected in series, whereby arated voltage of about 14.4 V can be realized, permitting the batterypack 1 to be used in business-use electronic apparatuses.

In addition, in the battery pack 1, the battery cells 8 are arranged intwo rows and four layers, so that the area of the lower surface 2 aserving as a mount surface in mounting into the battery mount part 5 ofthe electronic apparatus is made to be equal to the area occupied by twobattery cells 8 arranged side by side; thus, the insertion area can bereduced.

Further, in the battery pack 1, the partition member 20 is fitted withthe display circuit board 60 on the upper side of the fourth batterycell 8 d and the eighth battery cell 8 h, so that the electronic partsmounted on the display circuit board 60 such as the light emittingdevices 61 and the residual charge display switch element 62 can beexposed to the exterior from the upper surface 2 f of the upper cover 3.

Besides, in the battery pack 1, the display circuit board 60 iselectrically connected to the board connection tab part 33 d formed at asubstantially middle position of the continuous tab part 33 c of thethird electrode tab 33, and, further, the display circuit board 60 iselectrically connected to the main circuit board 50 through the flexibleflat cable 36. Therefore, the third electrode tab 33 can be electricallyconnected to the main circuit board 50 through the display circuit board60, without need for complicated wiring or the like.

Further, in the battery pack 1, the main circuit board 50 iselectrically connected through the first to fifth electrode tabs 31 to35 for electrical connection between the terminals of the battery cells8. Therefore, respective set voltages of the sets of parallel-connectedpaired battery cells 8 can be detected by the voltage detection unit 56in the main circuit board 50, and it is possible to check the residualbattery charges of the battery cells 8, the presence/absence of anabnormality in the battery cells 8, etc.

Incidentally, the battery packs 1, 100 are not limited to theconfiguration in which the four sets (a total number being eight) ofparallel-connected paired battery cells 8 are connected in series or thefour battery cells 8 are directly connected in series, for realizing arated voltage of about 14.4 V which is demanded for business-useelectronic apparatuses. For example, a configuration may be adopted inwhich four sets (a total number being twelve) of three-membered groupedbattery cells are connected in series to realize a rated voltage ofabout 14.4 V.

In addition, the application of the battery packs 1, 100 is not limitedto the application to the video camera 7 described above, and thebattery packs are applicable also to other electronic apparatuses forbusiness use.

Further, the application of the battery packs 1, 100 is not limited tothe application to business-use electronic apparatus described above,and the battery packs are applicable also to private-use electronicapparatuses.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A battery pack comprising: a plurality of cylindrical battery cellsarranged in a plurality of rows and a plurality of layers; a partitionmember for partitioning said battery cells; and a casing for containingsaid battery cells partitioned by said partition member; wherein thematerial thickness of said casing is set to be larger than the materialthickness of said partition member.
 2. The battery pack as set forth inclaim 1, wherein the material thickness of said casing is a thicknessconforming to the UL (stands for Underwriters Laboratories Inc.) 94Standard (fire retardancy of plastics).